Writing Equations of Lines

Exit Ticket

1) Write the equation of a line parallel to y=2x+9 that passes through (4,7).

• First find the slope!!!!

• The slope given is 2. Since the equation must be parallel the slope used must be 2.

1) Write the equation of a line parallel to y=2x+9 that passes through (4,7).

• Therefore m=2 and the point (4,7) are x and y respectively.

• Substitute y, m, and x in y=mx+b.7=2(4)+b (Note that the letter b stays in the equation. 9 is not used.)

Use this to find the new b!

1) Write the equation of a line parallel to y=2x+9 that passes through (4,7).

Use this to find the new b!

7=2(4)+b (Note that the letter b stays in the equation. 9 is not used.)

7 = 8+b-8 -8-1= b

1) Write the equation of a line parallel to y=2x+9 that passes through (4,7).

What is our new b???

b=-1

1) Write the equation of a line parallel to y=2x+9 that passes through (4,7).

b=-1So our equation is…

y= 2x+ -1 m b

2) Write an equation that is perpendicular to y= -1/4 x+1 and goes through ( 4,2).

• First find the slope!!!!

• The given slope is -1/4.

• What is the perpendicular slope??????

•m= - ¼ perpendicular m= + 4

2) Write an equation that is perpendicular to y= -1/4 x+1 and goes through ( 4,2).

• With m= 4 and the point (4,2) we can write the equation.

• Write the formula y=mx+b.

• Then substitute y, m, and x and then solve for

the new b.

2) Write an equation that is perpendicular to y= -1/4 x+1 and goes through ( 4,2).

• With m= 4 and the point (4,2) we can write the equation.

• Then substitute y, m, and x and then solve for

the new b.• y=mx+b• 2=4(4)+b

2) Write an equation that is perpendicular to y= -1/4 x+1 and goes through ( 4,2).

• y=mx+b• 2=4(4)+b

2 = 16+b - 16 -16- 14=b

2) Write an equation that is perpendicular to y= -1/4 x+1 and goes through ( 4,2).

B=4So our equation is…

y= 4x+ -14 m b