Question

Complete the equation of the line through (2,1) and (5,-8)

Answer 1

First we calculate the slope (which is called "m".

Slope = m = (Y2 -Y1) ÷ (X2 -X1)

m = (-8 -1) / (5 -2) = -9 / 3 = -3

We next fill in this equation: b = y -mx

We know m = -3 and we can choose a point (2, 1) to calculate "b"

b = 1 --3 * 2 b = 7

Putting this into y = mx +b

y = -3x +7