Question

The points (−3, r)  and (2, 1) lie on a line with slope −2 . Find the missing coordinate r .

Answer 1

We can use point slope form to solve for this.

y - 1 = -2(x - 2)
Simplify.
y - 1 = -2x + 4
Add 1 to both sides.
y = -2x + 5

Now, we can input -3 for x and solve for y, or r in this case.

y = -2(-3) + 5
y = 6 + 5
y = 11

r = 11