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Page 1: 2.4 slopes and difference quotient

Slopes and the Difference Quotient

http://www.lahc.edu/math/precalculus/math_260a.html

Page 2: 2.4 slopes and difference quotient

In order to discuss mathematics precisely, basic geometric information and formulas concerning graphs are given in function notation.

Slopes and the Difference Quotient

Page 3: 2.4 slopes and difference quotient

Given x, the output of a function is denoted as y or as f(x).

In order to discuss mathematics precisely, basic geometric information and formulas concerning graphs are given in function notation.

Slopes and the Difference Quotient

Page 4: 2.4 slopes and difference quotient

Given x, the output of a function is denoted as y or as f(x). Hence the coordinate of a general point P on the graph is often denoted as (x, f(x)).

In order to discuss mathematics precisely, basic geometric information and formulas concerning graphs are given in function notation.

Slopes and the Difference Quotient

Page 5: 2.4 slopes and difference quotient

Given x, the output of a function is denoted as y or as f(x). Hence the coordinate of a general point P on the graph is often denoted as (x, f(x)).

x

P=(x, f(x))

In order to discuss mathematics precisely, basic geometric information and formulas concerning graphs are given in function notation.

y= f(x)

Slopes and the Difference Quotient

Page 6: 2.4 slopes and difference quotient

Given x, the output of a function is denoted as y or as f(x). Hence the coordinate of a general point P on the graph is often denoted as (x, f(x)).

In order to discuss mathematics precisely, basic geometric information and formulas concerning graphs are given in function notation.

x

P=(x, f(x))

y= f(x)

f(x)

Note that the f(x) = the height of the point P.

Slopes and the Difference Quotient

Page 7: 2.4 slopes and difference quotient

Given x, the output of a function is denoted as y or as f(x). Hence the coordinate of a general point P on the graph is often denoted as (x, f(x)).

Let h be a small positive value, so x+h is a point close to x,

In order to discuss mathematics precisely, basic geometric information and formulas concerning graphs are given in function notation.

x

P=(x, f(x))

y= f(x)

f(x)

Note that the f(x) = the height of the point P.

Slopes and the Difference Quotient

Page 8: 2.4 slopes and difference quotient

Given x, the output of a function is denoted as y or as f(x). Hence the coordinate of a general point P on the graph is often denoted as (x, f(x)).

x

P=(x, f(x))

Note that the f(x) = the height of the point P.

Let h be a small positive value, so x+h is a point close to x,

x+h

In order to discuss mathematics precisely, basic geometric information and formulas concerning graphs are given in function notation.

f(x)

y= f(x)

Slopes and the Difference Quotient

Page 9: 2.4 slopes and difference quotient

Given x, the output of a function is denoted as y or as f(x). Hence the coordinate of a general point P on the graph is often denoted as (x, f(x)).

x

P=(x, f(x))

Note that the f(x) = the height of the point P.

Let h be a small positive value, so x+h is a point close to x,

x+h

then f(x+h) is the output for x+h, and (x+h, f(x+h)) represents the corresponding point, say Q, on the graph.

In order to discuss mathematics precisely, basic geometric information and formulas concerning graphs are given in function notation.

f(x)

y= f(x)

Slopes and the Difference Quotient

Page 10: 2.4 slopes and difference quotient

Given x, the output of a function is denoted as y or as f(x). Hence the coordinate of a general point P on the graph is often denoted as (x, f(x)).

x

P=(x, f(x))

Note that the f(x) = the height of the point P.

Let h be a small positive value, so x+h is a point close to x,

x+h

then f(x+h) is the output for x+h, and (x+h, f(x+h)) represents the corresponding point, say Q, on the graph.

In order to discuss mathematics precisely, basic geometric information and formulas concerning graphs are given in function notation.

Q=(x+h, f(x+h))

f(x)

y= f(x)

Slopes and the Difference Quotient

Page 11: 2.4 slopes and difference quotient

Given x, the output of a function is denoted as y or as f(x). Hence the coordinate of a general point P on the graph is often denoted as (x, f(x)).

x

P=(x, f(x))

Note that the f(x) = the height of the point P.

Let h be a small positive value, so x+h is a point close to x,

x+h

then f(x+h) is the output for x+h, and (x+h, f(x+h)) represents the corresponding point, say Q, on the graph.

In order to discuss mathematics precisely, basic geometric information and formulas concerning graphs are given in function notation.

Note that the f(x+h) = the height of the point Q.

Q=(x+h, f(x+h))

f(x) f(x+h)

y= f(x)

Slopes and the Difference Quotient

Page 12: 2.4 slopes and difference quotient

Recall that if (x1, y1) and (x2, y2) are two points then the slope m of the line connecting them is Δy m =

y2 – y1 =

x2 – x1 Δx

Slopes and the Difference Quotient

Page 13: 2.4 slopes and difference quotient

Recall that if (x1, y1) and (x2, y2) are two points then the slope m of the line connecting them is Δy m =

y2 – y1 =

x2 – x1 Δx

Let (x1,y1) = P = (x, f(x)) and (x2,y2) = Q = (x+h, f(x+h)) as shown in the picture,

Slopes and the Difference Quotient

Page 14: 2.4 slopes and difference quotient

Recall that if (x1, y1) and (x2, y2) are two points then the slope m of the line connecting them is

x

P=(x, f(x))

x+h

Q=(x+h, f(x+h))

Δy m =

y2 – y1 =

x2 – x1 Δx

Let (x1,y1) = P = (x, f(x)) and (x2,y2) = Q = (x+h, f(x+h)) as shown in the picture,

Slopes and the Difference Quotient

Page 15: 2.4 slopes and difference quotient

Recall that if (x1, y1) and (x2, y2) are two points then the slope m of the line connecting them is

x

P=(x, f(x))

x+h

Q=(x+h, f(x+h))

Δy m =

y2 – y1 =

x2 – x1 Δx

Let (x1,y1) = P = (x, f(x)) and (x2,y2) = Q = (x+h, f(x+h)) as shown in the picture, then the slope of the cord connecting P and Q (in function notation) is

Slopes and the Difference Quotient

Page 16: 2.4 slopes and difference quotient

Recall that if (x1, y1) and (x2, y2) are two points then the slope m of the line connecting them is

x

P=(x, f(x))

x+h

Q=(x+h, f(x+h))

Δy m =

y2 – y1 =

x2 – x1 Δx

Let (x1,y1) = P = (x, f(x)) and (x2,y2) = Q = (x+h, f(x+h)) as shown in the picture, then the slope of the cord connecting P and Q (in function notation) is

Δy m =

f(x+h) – f(x) =

(x+h) – x Δx

Slopes and the Difference Quotient

Page 17: 2.4 slopes and difference quotient

Recall that if (x1, y1) and (x2, y2) are two points then the slope m of the line connecting them is

x

P=(x, f(x))

x+h

Q=(x+h, f(x+h))

Δy m =

y2 – y1 =

x2 – x1 Δx

Let (x1,y1) = P = (x, f(x)) and (x2,y2) = Q = (x+h, f(x+h)) as shown in the picture, then the slope of the cord connecting P and Q (in function notation) is

Δy m =

f(x+h) – f(x) =

(x+h) – x Δx or m =

f(x+h) – f(x) h

Slopes and the Difference Quotient

Page 18: 2.4 slopes and difference quotient

Recall that if (x1, y1) and (x2, y2) are two points then the slope m of the line connecting them is

x

P=(x, f(x))

x+h

Q=(x+h, f(x+h))

Δy m =

y2 – y1 =

x2 – x1 Δx

Let (x1,y1) = P = (x, f(x)) and (x2,y2) = Q = (x+h, f(x+h)) as shown in the picture, then the slope of the cord connecting P and Q (in function notation) is

Δy m =

f(x+h) – f(x) =

(x+h) – x Δx or m =

f(x+h) – f(x) h

This is the "difference quotient" formula for slopes

Slopes and the Difference Quotient

Page 19: 2.4 slopes and difference quotient

Recall that if (x1, y1) and (x2, y2) are two points then the slope m of the line connecting them is

x

P=(x, f(x))

x+h

Q=(x+h, f(x+h))

Δy m =

y2 – y1 =

x2 – x1 Δx

Let (x1,y1) = P = (x, f(x)) and (x2,y2) = Q = (x+h, f(x+h)) as shown in the picture, then the slope of the cord connecting P and Q (in function notation) is

Δy m =

f(x+h) – f(x) =

(x+h) – x Δx or m =

f(x+h) – f(x) h

because f(x+h) – f(x) = difference in heightThis is the "difference quotient" formula for slopes

Slopes and the Difference Quotient

Page 20: 2.4 slopes and difference quotient

Recall that if (x1, y1) and (x2, y2) are two points then the slope m of the line connecting them is

x

P=(x, f(x))

x+h

Q=(x+h, f(x+h))

Δy m =

y2 – y1 =

x2 – x1 Δx

Let (x1,y1) = P = (x, f(x)) and (x2,y2) = Q = (x+h, f(x+h)) as shown in the picture, then the slope of the cord connecting P and Q (in function notation) is

Δy m =

f(x+h) – f(x) =

(x+h) – x Δx or m =

f(x+h) – f(x) h

f(x+h)–f(x) = Δy

because f(x+h) – f(x) = difference in heightThis is the "difference quotient" formula for slopes

Slopes and the Difference Quotient

Page 21: 2.4 slopes and difference quotient

Recall that if (x1, y1) and (x2, y2) are two points then the slope m of the line connecting them is

x

P=(x, f(x))

x+h

Q=(x+h, f(x+h))

Δy m =

y2 – y1 =

x2 – x1 Δx

Let (x1,y1) = P = (x, f(x)) and (x2,y2) = Q = (x+h, f(x+h)) as shown in the picture, then the slope of the cord connecting P and Q (in function notation) is

Δy m =

f(x+h) – f(x) =

(x+h) – x Δx or m =

f(x+h) – f(x) h

f(x+h)–f(x) = Δy

because f(x+h) – f(x) = difference in height andh = (x+h) – x = difference in the x's, as shown.

This is the "difference quotient" formula for slopes.

Slopes and the Difference Quotient

Page 22: 2.4 slopes and difference quotient

Recall that if (x1, y1) and (x2, y2) are two points then the slope m of the line connecting them is

x

P=(x, f(x))

x+h

Q=(x+h, f(x+h))

Δy m =

y2 – y1 =

x2 – x1 Δx

Let (x1,y1) = P = (x, f(x)) and (x2,y2) = Q = (x+h, f(x+h)) as shown in the picture, then the slope of the cord connecting P and Q (in function notation) is

Δy m =

f(x+h) – f(x) =

(x+h) – x Δx or m =

f(x+h) – f(x) h

h=Δx

f(x+h)–f(x) = Δy

because f(x+h) – f(x) = difference in height andh = (x+h) – x = difference in the x's, as shown.

This is the "difference quotient" formula for slopes.

Slopes and the Difference Quotient

Page 23: 2.4 slopes and difference quotient

Example A. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)) with x = 2 and h = 0.2.

Slopes and the Difference Quotient

Page 24: 2.4 slopes and difference quotient

Example A. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)) with x = 2 and h = 0.2.

We want the slope of the cord connecting the points whose x-coordinates are x = 2 and x + h = 2 + h = 2.2.

Slopes and the Difference Quotient

Page 25: 2.4 slopes and difference quotient

Example A. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)) with x = 2 and h = 0.2.

f(x+h) – f(x) h

Using the difference quotient, the slope is

We want the slope of the cord connecting the points whose x-coordinates are x = 2 and x + h = 2 + h = 2.2

Slopes and the Difference Quotient

Page 26: 2.4 slopes and difference quotient

Example A. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)) with x = 2 and h = 0.2.

f(x+h) – f(x) h

Using the difference quotient, the slope is

We want the slope of the cord connecting the points whose x-coordinates are x = 2 and x + h = 2 + h = 2.2

f(2.2) – f(2) =

Slopes and the Difference Quotient

Page 27: 2.4 slopes and difference quotient

Example A. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)) with x = 2 and h = 0.2.

f(x+h) – f(x) h

Using the difference quotient, the slope is

We want the slope of the cord connecting the points whose x-coordinates are x = 2 and x + h = 2 + h = 2.2

f(2.2) – f(2) 0.2

=

Slopes and the Difference Quotient

Page 28: 2.4 slopes and difference quotient

Example A. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)) with x = 2 and h = 0.2.

f(x+h) – f(x) h

Using the difference quotient, the slope is

We want the slope of the cord connecting the points whose x-coordinates are x = 2 and x + h = 2 + h = 2.2

f(2.2) – f(2) 0.2

=

=2.44 – 2

0.2

Slopes and the Difference Quotient

Page 29: 2.4 slopes and difference quotient

Example A. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)) with x = 2 and h = 0.2.

f(x+h) – f(x) h

Using the difference quotient, the slope is

We want the slope of the cord connecting the points whose x-coordinates are x = 2 and x + h = 2 + h = 2.2

f(2.2) – f(2) 0.2

=

=2.44 – 2

0.2 =0.44 0.2

Slopes and the Difference Quotient

Page 30: 2.4 slopes and difference quotient

Example A. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)) with x = 2 and h = 0.2.

f(x+h) – f(x) h

Using the difference quotient, the slope is

We want the slope of the cord connecting the points whose x-coordinates are x = 2 and x + h = 2 + h = 2.2

f(2.2) – f(2) 0.2

=

=2.44 – 2

0.2= 2.2

=0.44 0.2

Slopes and the Difference Quotient

Page 31: 2.4 slopes and difference quotient

Example A. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)) with x = 2 and h = 0.2.

f(x+h) – f(x) h

Using the difference quotient, the slope is

We want the slope of the cord connecting the points whose x-coordinates are x = 2 and x + h = 2 + h = 2.2

f(2.2) – f(2) 0.2

=

=2.44 – 2

0.2= 2.2

(2.2, 2.44)

(2, 2)

2 2.2

=0.44 0.2

Slopes and the Difference Quotient

Page 32: 2.4 slopes and difference quotient

Example A. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)) with x = 2 and h = 0.2.

f(x+h) – f(x) h

Using the difference quotient, the slope is

We want the slope of the cord connecting the points whose x-coordinates are x = 2 and x + h = 2 + h = 2.2

f(2.2) – f(2) 0.2

=

=2.44 – 2

0.2= 2.2

(2.2, 2.44)

(2, 2)

2 2.2

=0.44 0.2

0.44

0.2

slope m = 2.2

Slopes and the Difference Quotient

Page 33: 2.4 slopes and difference quotient

b. Given f(x) = x2 – 2x + 2, simplify the formula for the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)).

Slopes and the Difference Quotient

Page 34: 2.4 slopes and difference quotient

b. Given f(x) = x2 – 2x + 2, simplify the formula for the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)). We are to simplify the difference quotient formula with f(x) = x2 – 2x + 2

Slopes and the Difference Quotient

Page 35: 2.4 slopes and difference quotient

b. Given f(x) = x2 – 2x + 2, simplify the formula for the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)).

f(x+h) – f(x) h

We are to simplify the difference quotient formula with f(x) = x2 – 2x + 2

=

(x+h)2 – 2(x+h) + 2 – [ x2 – 2x + 2]h

Slopes and the Difference Quotient

Page 36: 2.4 slopes and difference quotient

b. Given f(x) = x2 – 2x + 2, simplify the formula for the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)).

f(x+h) – f(x) h

We are to simplify the difference quotient formula with f(x) = x2 – 2x + 2

=

(x+h)2 – 2(x+h) + 2 – [ x2 – 2x + 2]h

2xh – 2h + h2 h

=

Slopes and the Difference Quotient

Page 37: 2.4 slopes and difference quotient

b. Given f(x) = x2 – 2x + 2, simplify the formula for the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)).

f(x+h) – f(x) h

We are to simplify the difference quotient formula with f(x) = x2 – 2x + 2

=

(x+h)2 – 2(x+h) + 2 – [ x2 – 2x + 2]h

2xh – 2h + h2 h

= 2x – 2 + h. =

Slopes and the Difference Quotient

Page 38: 2.4 slopes and difference quotient

Another version of the difference quotient formula is to use pointsP = (a, f(a)) and Q= (b, f(b)).

b. Given f(x) = x2 – 2x + 2, simplify the formula for the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)).

f(x+h) – f(x) h

We are to simplify the difference quotient formula with f(x) = x2 – 2x + 2

=

(x+h)2 – 2(x+h) + 2 – [ x2 – 2x + 2]h

2xh – 2h + h2 h

= 2x – 2 + h. =

Slopes and the Difference Quotient

Page 39: 2.4 slopes and difference quotient

Another version of the difference quotient formula is to use pointsP = (a, f(a)) and Q= (b, f(b)). We get

Δy m =

f(b) – f(a) =

b – a Δx

b. Given f(x) = x2 – 2x + 2, simplify the formula for the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)).

f(x+h) – f(x) h

We are to simplify the difference quotient formula with f(x) = x2 – 2x + 2

=

(x+h)2 – 2(x+h) + 2 – [ x2 – 2x + 2]h

2xh – 2h + h2 h

= 2x – 2 + h. =

Slopes and the Difference Quotient

Page 40: 2.4 slopes and difference quotient

Another version of the difference quotient formula is to use pointsP = (a, f(a)) and Q= (b, f(b)). We get

a

P=(a, f(a))

b

Q=(b, f(b))

Δy m =

f(b) – f(a) =

b – a Δx

b. Given f(x) = x2 – 2x + 2, simplify the formula for the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)).

f(x+h) – f(x) h

We are to simplify the difference quotient formula with f(x) = x2 – 2x + 2

=

(x+h)2 – 2(x+h) + 2 – [ x2 – 2x + 2]h

2xh – 2h + h2 h

= 2x – 2 + h. =

Slopes and the Difference Quotient

Page 41: 2.4 slopes and difference quotient

Another version of the difference quotient formula is to use pointsP = (a, f(a)) and Q= (b, f(b)). We get

a

P=(a, f(a))

b

Q=(b, f(b))

Δy m =

f(b) – f(a) =

b – a Δx

b-a=Δx

f(b)–f(a) = Δy

b. Given f(x) = x2 – 2x + 2, simplify the formula for the slope of the cord connecting the points (x, f(x)) and (x+h, f(x+h)).

f(x+h) – f(x) h

We are to simplify the difference quotient formula with f(x) = x2 – 2x + 2

=

(x+h)2 – 2(x+h) + 2 – [ x2 – 2x + 2]h

2xh – 2h + h2 h

= 2x – 2 + h. =

Slopes and the Difference Quotient

Page 42: 2.4 slopes and difference quotient

Example B. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (a, f(a)) and (b,f(b)) with a = 3 and b = 5.

Slopes and the Difference Quotient

Page 43: 2.4 slopes and difference quotient

Example B. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (a, f(a)) and (b,f(b)) with a = 3 and b = 5.

We want the slope of the cord connecting the points whose x-coordinates are a = 3 and b = 5

Slopes and the Difference Quotient

Page 44: 2.4 slopes and difference quotient

Example B. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (a, f(a)) and (b,f(b)) with a = 3 and b = 5.

f(b) – f(a) b – a

Using the formula, the slope is

We want the slope of the cord connecting the points whose x-coordinates are a = 3 and b = 5

Slopes and the Difference Quotient

Page 45: 2.4 slopes and difference quotient

Example B. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (a, f(a)) and (b,f(b)) with a = 3 and b = 5.

f(b) – f(a) b – a

Using the formula, the slope is

We want the slope of the cord connecting the points whose x-coordinates are a = 3 and b = 5

f(5) – f(3) 5 – 3

=

Slopes and the Difference Quotient

Page 46: 2.4 slopes and difference quotient

Example B. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (a, f(a)) and (b,f(b)) with a = 3 and b = 5.

f(b) – f(a) b – a

Using the formula, the slope is

We want the slope of the cord connecting the points whose x-coordinates are a = 3 and b = 5

f(5) – f(3) 5 – 3

=

=17 – 5

2

Slopes and the Difference Quotient

Page 47: 2.4 slopes and difference quotient

Example B. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (a, f(a)) and (b,f(b)) with a = 3 and b = 5.

f(b) – f(a) b – a

Using the formula, the slope is

We want the slope of the cord connecting the points whose x-coordinates are a = 3 and b = 5

f(5) – f(3) 5 – 3

=

=17 – 5

2

= 6=12 2

Slopes and the Difference Quotient

Page 48: 2.4 slopes and difference quotient

Example B. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (a, f(a)) and (b,f(b)) with a = 3 and b = 5.

f(b) – f(a) b – a

Use the formula, the slope is

We want the slope of the cord connecting the points whose x-coordinates are a = 3 and b = 5

f(5) – f(3) 5 – 3

=

=17 – 5

2

= 6

(5, 17)

(3, 5)

3 5=12 2

Slopes and the Difference Quotient

Page 49: 2.4 slopes and difference quotient

Example B. a. Given f(x) = x2 – 2x + 2, find the slope of the cord connecting the points (a, f(a)) and (b,f(b)) with a = 3 and b = 5.

f(b) – f(a) b – a

Use the formula, the slope is

We want the slope of the cord connecting the points whose x-coordinates are a = 3 and b = 5

f(5) – f(3) 5 – 3

=

=17 – 5

2

= 6

(5, 17)

(3, 5)

3 5=12 2

12

2

slope m = 6

Slopes and the Difference Quotient

Page 50: 2.4 slopes and difference quotient

b. Given f(x) = x2 – 2x + 2, simplify the difference quotient slope of the cord connecting the points (a, f(a)) and (b, f(b)).

(b, f(b))

(a, f(a))

a b

f(b)-f(a)

b-a

Slopes and the Difference Quotient

Page 51: 2.4 slopes and difference quotient

b. Given f(x) = x2 – 2x + 2, simplify the difference quotient slope of the cord connecting the points (a, f(a)) and (b, f(b)).

f(b) – f(a) b – a

We are to simplify the 2nd form of the difference quotient formula with f(x) = x2 – 2x + 2

(b, f(b))

(a, f(a))

a b

f(b)-f(a)

b-a

Slopes and the Difference Quotient

Page 52: 2.4 slopes and difference quotient

b. Given f(x) = x2 – 2x + 2, simplify the difference quotient slope of the cord connecting the points (a, f(a)) and (b, f(b)).

f(b) – f(a) b – a

We are to simplify the 2nd form of the difference quotient formula with f(x) = x2 – 2x + 2

=

b2 – 2b + 2 – [ a2 – 2a + 2]b – a

(b, f(b))

(a, f(a))

a b

f(b)-f(a)

b-a

Slopes and the Difference Quotient

Page 53: 2.4 slopes and difference quotient

b. Given f(x) = x2 – 2x + 2, simplify the difference quotient slope of the cord connecting the points (a, f(a)) and (b, f(b)).

f(b) – f(a) b – a

We are to simplify the 2nd form of the difference quotient formula with f(x) = x2 – 2x + 2

=

b2 – 2b + 2 – [ a2 – 2a + 2]b – a

=

b2 – a2 – 2b + 2a b – a

(b, f(b))

(a, f(a))

a b

f(b)-f(a)

b-a

Slopes and the Difference Quotient

Page 54: 2.4 slopes and difference quotient

b. Given f(x) = x2 – 2x + 2, simplify the difference quotient slope of the cord connecting the points (a, f(a)) and (b, f(b)).

f(b) – f(a) b – a

We are to simplify the 2nd form of the difference quotient formula with f(x) = x2 – 2x + 2

=

b2 – 2b + 2 – [ a2 – 2a + 2]b – a

=

b2 – a2 – 2b + 2a b – a

=

(b – a)(b + a) – 2(b – a)b – a

(b, f(b))

(a, f(a))

a b

f(b)-f(a)

b-a

Slopes and the Difference Quotient

Page 55: 2.4 slopes and difference quotient

b. Given f(x) = x2 – 2x + 2, simplify the difference quotient slope of the cord connecting the points (a, f(a)) and (b, f(b)).

f(b) – f(a) b – a

We are to simplify the 2nd form of the difference quotient formula with f(x) = x2 – 2x + 2

=

b2 – 2b + 2 – [ a2 – 2a + 2]b – a

=

b2 – a2 – 2b + 2a b – a

=

(b – a)(b + a) – 2(b – a)b – a

=

(b – a) [(b + a) – 2]b – a

(b, f(b))

(a, f(a))

a b

f(b)-f(a)

b-a

Slopes and the Difference Quotient

Page 56: 2.4 slopes and difference quotient

b. Given f(x) = x2 – 2x + 2, simplify the difference quotient slope of the cord connecting the points (a, f(a)) and (b, f(b)).

f(b) – f(a) b – a

We are to simplify the 2nd form of the difference quotient formula with f(x) = x2 – 2x + 2

=

b2 – 2b + 2 – [ a2 – 2a + 2]b – a

=

b2 – a2 – 2b + 2a b – a

=

(b – a)(b + a) – 2(b – a)b – a

=

(b – a) [(b + a) – 2]b – a

= b + a – 2

(b, f(b))

(a, f(a))

a b

f(b)-f(a)

b-a

Slopes and the Difference Quotient

Page 57: 2.4 slopes and difference quotient

HWGiven the following f(x), x, and h find f(x+h) – f(x)1. y = 3x+2, x= 2, h = 0.1 2. y = -2x + 3, x= -4, h = 0.053. y = 2x2 + 1, x = 1, h = 0.1 4. y = -x2 + 3, x= -2, h = -0.2

Given the following f(x), simplify Δy = f(x+h) – f(x)5. y = 3x+2 6. y = -2x + 37. y = 2x2 + 1 8. y = -x2 + 3

Simplify the difference quotient: f(x+h) – f(x) h

of the following functions. (Make sure the factor “h” in the denominator is cleared away in the answer)

9. y = -4x + 3 10. y = mx + b

11. y = 3x2 – 2x +2 12. y = -2x2 + 3x -1

Slopes and the Difference Quotient

13. y = 14. y =

2 x + 3

2x – 1 x – 2

16. y = (3 – x)1/215. y = x1/2