Question:
Let $f(x)=\sin ^{-1} x$ and $g(x)=\frac{x^{2}-x-2}{2 x^{2}-x-6}$. If $g(2)=\lim _{x \rightarrow 2} g(x)$, then the domain of the function $f \circ g$ is :
Correct Option: , 3
Solution:
Domain of $f \circ g(x)=\sin ^{-1}(g(x))$
$\Rightarrow|g(x)| \leq 1 \quad, \quad g(2)=\frac{3}{7}$
$\left|\frac{x^{2}-x-2}{2 x^{2}-x-6}\right| \leq 1$
$\left|\frac{(x+1)(x-2)}{(2 x+3)(x-2)}\right| \leq 1$
$\frac{x+1}{2 x+3} \leq 1$ and $\frac{x+1}{2 x+3} \geq-1$
$\frac{x+1-2 x-3}{2 x+3} \leq 0$ and $\frac{x+1+2 x+3}{2 x+3} \geq 0$
$\frac{x+2}{2 x+3} \geq 0$ and $\frac{3 x+4}{2 x+3} \geq 0$
$x \in(-\infty,-2] \cup\left[-\frac{4}{3}, \infty\right)$