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Solving &
GraphingInequalities
Half - Plane
Objective- To graph inequalities on the coordinate plane.
Recall…Graph n < 3 on a number line.
-3 -2 -1 0 1 2 3 4
Graph y > 3 on the coordinate plane.
x
y
Graph x -2 on the coordinate plane.
x
y
How to graph a line
• Write the inequality as an equation• E.g. y ≥ - 3x + 2 y = -3x + 2• Make a table of x,y values• x y = -3x+2• 0 -3(0) + 2 = 2 (0,2)• 1 -3(1) +2 = -1 (1, -1)• 2 -3(2) +2 = -4 (2, -4)• Graph these points and draw a line.
Graph y -3x + 2 on the coordinate plane.
x
y
Boundary Line
y = -3x + 2
a = -3
b = 2
31
Test a point not on the linetest (0,0)
0 -3(0) + 2Not true!
Graph y -3x + 2 on the coordinate plane.
x
y
Instead of testing a point
If in y = ax + b form...
Shade up
Shadedown
Solid line
Dashed line
> <
Graph on the coordinate plane.3x - 4y > 12-3x -3x-4y > -3x + 12-4 -4y < x - 3
34
a =
b = -3
34
Boundary Linex
y
ProblemIf you have less than $5.00 in nickels and dimes, find an inequality and sketch a graph to describe how many of each coin you have.
Let n = # of nickelsLet d = # of dimes
0.05 n + 0.10 d < 5.00 or 5 n + 10 d < 500
5n + 10d < 500n d
0 50
100 0
0 10 20 30 40 50 60 70 80 90 100n
d
60
50
40
30
20
10
0
Find the Vertex(es) or Vertices
• What were the (x,y) coordinates for the triangle of constraints we just made?
Optimization
• Optimization is when we use a polygon of constraints (the shape we made with the inequalities) to find out the maximum or minimum value of another equation.
• We need the vertices: (0,50) (100,0) (0,0)• We substitute them into another equation to
and calculate the value.
Optimization
x y Optimization Equation
P = 3x – 2 y0 0 3(0) -2(0)
= 00 50 3(0) -2(50)
= -100 Min100 0 3(100) -2(0)
= 300 Max
Check-up
AssignmentPage 43, Q. 3,4,6
**Will need graph paper