#### Answer

$x=-9,5$ are the excluded values of $x$ from the domain.

#### Work Step by Step

As per given question: $f(x)=\dfrac{3}{x^2+4x-45}$
Need to use factorization to solve the quadratic equation .
$\dfrac{3}{x^2+4x-45}=0$
or, $\dfrac{3}{x^2+9x-4x-45}=0$
or, $\dfrac{3}{(x+9)(x-5)}=0$
This implies that $x=-9,5$ the denominator will get zero.
Hence, $x=-9,5$ are the excluded values of $x$ from the domain.