Question

Solve 4r2 – 9 = 91.
A:{±3}
B:{±4}
C:{±5}
D:{±6}

Answer 1

Take the root of both sides and solve. The answer is C.

Answer 2

4r² - 9 = 91
4r² = 91 + 9
4r² = 100
r² = 25
r = + / - 5

Correct option C