Question

Given that the line y=ax+b passes through the points A(0; 3) and B(-2;7), how do I find the values of a and b?

Answer 1

First you have find the slope (a) in order to find the value of the y intercept (b).

To compute the slope, you simply have to find the difference of y coordinates and divide them by the difference of x coordinates:

a = (y2-y1)/(x2-x1)
a = (7-3)/(-2–0)
a = 4/-2
a = -2

To compute the y intercept denoted by b, we substitute the value of a with -2 in the formula and choose any point (x,y) and substitute their values in the formula as well. Like so:

I choose point A:

3 = (-2)(0) + b
3 = b