Question

If $f:R\to R$ and $g:R\to R$ defined by f(x) = 2x + 3 and $g(x)=x^2+7$, then the value of x for which f(g(x)) = 25

• A. $\pm 1$
• B. $\pm 2$
• C. $\pm 3$
• D. $\pm 4$

Answer 1

Answer: (B)

$f(g(x))=f(x^2+7)=2(x^2+7)+3=25$
$\Rightarrow 2x^2=8\Rightarrow x=\pm 2$