Question

The points (1,-10) and (r,-2) lie on a line with slope 2. Find the missing coordinate r

Answer 1

m = y₂-y₁ / x₂ - x₁


2 = -2 - (-10) / r - 1

2 = 8 / r-1

²/₁ = ⁸/r-1

(r-1)(2) = (8)(1)

2r - 2 = 8

2r = 8 + 2

2r = 10

r = 10 ÷ 2

r = 5