The points (6, −4) and (10, r) lie on a line with slope −3. Find the missing coordinate r.

Answer 1

We will be using slope formula

Slope = (y2 - y1)/(x2 - x1)

Slope = -3 , x1 =6, x2 =10, y1 = -4, y2 = r

-3 = (r + 4)/(10 - 6)

-3 = (r+4)/4

cross multiply r+4 = -12

r = -12-4 , r = -16

Answer 2

Use the definition of slope:

(r + 4) = -3(10 - 6)