Question

How do u do this??????

Answer 1

f(x^2) = x^2 - 3

5f(x^2) = 5x^2 - 15 = 2x - 8

Placing all the terms on the left side, we get:

5x^2 - 2x - 7 = 0 which factorises to

(5x - 7)(x + 1) = 0

So, x = 7/5 or x = -1

But x is non-negative, so x = 7/5 = 1 2/5

C is the answer.