Problem 7 - Entrance Test

If f(x)=√x and g(x)=x²-9, for which x is f(g(x)) defined?

A. x≤3 or x≥3B. x≥3C. x≤-3 or x≥3D. all real numbers

Correct: C

f(g(x)) defined when g(x)≥0 → x²-9≥0 → x≤-3 or x≥3.