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