y = mx + b

m = ?

+2

+2

+1

m = = 221

b = ?b = -3

y = 2x - 3

+1

y-intercept

Writing Equations of Lines

y = mx + b

Writing Equations of Lines

Find the equation of the line with a slope of –2/3 and a y-intercept of 1

Find the equation of the line with a slope of –2/3 and a y-intercept of 1

y = x + 123

y = mx + b

+2 -3 +3

-2

y = mx + b

y = x + 123

Writing Equations of Lines

Find the equation of the line throughthe points (-3,-4) and (3,-1).

m = ? b = ?

m = y2 – y1

x2 – x1

-1 – -43 – -3=

m = 36 =

12

y = mx + b

m = 12

-1 = (3) + b12

-1 = + b325

2 = b

b = 52

y = x – 12

52

Change in yChange in x

Writing the Equation of a Line

                       

                       

                       

                       

                       

                       

                       

                       

                       

                       

                       

                       

riserun

Slope = = 53

y = mx + b(4,3) 3 = 5/3(4) + b

3 = 20/3 + b-20/3

-11/3 = b-3.67 = b

y = 5/3x – 11/3

Writing Equations of Lines

Find the equation of the line throughthe points (1,-2) and (-4,1).

Point – Slope Form

m = y2 – y1

x2 – x1y – y1 = m(x – x1)

derived from

We still need the slopem =

1 – -2-4 – 1

35=

y – -2 = (x – 1)35

y – -2 = x + 35

35

-2 -2

y = - x – 35

75

Check it out on the calculator

Writing Equations of Lines

Write the equation of the line throughThe point (1, 2) and parallel to the lineY = 1/3x – 4.

m = ?m = 1/3

y – 2 = 1/3(x – 1)

y – 2 = 1/3x – 1/3+2 +2

y = 1/3x + 5/3

m = y2 – y1

x2 – x1

Writing Equations of Lines

Find the equation of the line throughThe point (-3, -4) and perpendicular to theLine y = -2x + 1.

y + 4 = 1/2(x + 3)y + 4 = 1/2x + 3/2-4 -4

y = 1/2x – 5/2

m = ?m = 1/2

m = y2 – y1

x2 – x1