Which is an equation of the line that passes through (-4,-2) and (4,2)?

a. y=1/2x
b. y=x-2
c. y=x+2
d. y=2x

The equation of a line is y = mx + b. Calculate the slope (m) from the 2 points.

m = (-2-2)/(-4-4) = -4/-8 = 1/2

We could stop here as only one answer has a slope of 1/2, namely A). But if you wanted to show that the y-intercept (b) was 0, you could use either of the points and substitute it into the equation of the line and solve for b.

(-4,-2):  
-2 = 1/2(-4) + b
-2 = -2 + b
0 = b

(4,2):
2 = 1/2(4) + b
2 = 2 + b
0 = b