Answer
$x=-4,7$ are the excluded values of $x$ from the domain.
Work Step by Step
As per given question: $f(x)=\dfrac{7}{x^2-3x-28}$
Need to use factorization to solve the quadratic equation .
$\dfrac{7}{x^2-3x-28}=0$
or, $\dfrac{7}{x^2-7x+4x-28}=0$
or, $\dfrac{7}{(x+4)(x-7)}=0$
This implies that $x=-4,7$ the denominator will get zero.
Hence, $x=-4,7$ are the excluded values of $x$ from the domain.
