Let f be a function with domain [–3, 5] and let g(x) = |3x + 4|. Then the domain of (fog)(x) is |
$\left(-3, \frac{1}{3}\right)$ $\left[-3, \frac{1}{3}\right]$ $\left[-3, \frac{1}{3}\right)$ None of these |
$\left[-3, \frac{1}{3}\right]$ |
$f(g(x))⇒-3≤|3x+4|≤5$ (Negative not considered due to modules) $⇒|3x+4|≤5$ so $-5≤3x+4≤5$ $(fog)(x)=f[g(x)]=f(|3 x+4|)$ $\Rightarrow-5 \leq 3 x+4 \leq 5$ $\Rightarrow-9 \leq 3 x \leq 1$ $\Rightarrow-3 \leq x \leq 1 / 3$ ∴ Domain of fog is $\left[-3, \frac{1}{3}\right]$ Hence (2) is the correct answer. |