Question

A line passes through the points (-1, 4) and (3, -8). A second line passes through

(-1,8) and (2, 11).
A) Write the equation of each line. Show all work.

Answer 1

y = -3x + 1, y = x + 9

Explanation:

An equation consists of a slope and the y-intercept. To find the slope, you need to plug the values into the slope formula.

y2 - y1/ x2 - x1

= -8 - 4/ 3 - (-1)

= -12/ 4

= -3

The slope of the first line is -3.

To find the y-intercept, you need to plug in either one of the coordinates into the equation, y = -3x + b

-8 = -3(3) + b

-8 = -9 + b

1 = b

The equation, for the first one, is y = -3x + 1

Line 2:

11 - 8/ 2 - (-1)

= 1

y = 1x + b

11 = 1(2) + b

11 = 2 + b

9 = b

y = x + 9