Question

I) (r + 1)(r + 9) = 16 r​

Answer 1

r = 3

Explanation:

(r + 1)(r + 9) = 16r ← expand left side using FOIL

r² + 9r + r + 9 = 16r

r² + 10r + 9 = 16r ( subtract 16r from both sides )

r² - 6r + 9 = 0

(r - 3)² = 0 , then

r - 3 = 0 ( add 3 to both sides )

r = 3