For eaplefunction, find the value$($s$)$ where the function is not defined. Then, find the domalo ef the function.

$($a$)f(x)=\frac{3-x^2}{1-e^3-x^2}$

$x=$

$$

$($b$)(x)=\frac{5x}{x^{2}21}$

$x=$

$$