Answer
$c=-4,8$
Work Step by Step
Given: $f(c)=c^2-4c-27$
Plug $f(c)=5$ then we have
$c^2-4c-27=5$
This can be written as: $c^2-4c-32=0$
Need to use factorization to solve the quadratic equation .
$c^2+4c-8c-32=5$
This implies $(c+4)(c-8)=0$
Now, $c+4=0 $ and $c-8=0$
Hence, $c=-4,8$
