Answer
$d = -22, d= -12$
Work Step by Step
Use either the square root method, the quadratic formula or factoring. $$
\begin{aligned}
105 & =5(17+d)^2-20 \\
105+20 & =5(17+d)^2 \\
125 & =5(17+d)^2 \\
25 & =(17+d)^2 \\
\pm \sqrt{25} & =17+d \\
\pm 5-17 & =d
\end{aligned}
$$ This gives: $$
\begin{aligned}
d & =-5-17 \\
& =-22\\
d & =5-17 \\
& =-12.
\end{aligned}
$$ Define the following function and plot it. We see that the zeros are where they should be.
$$
f(d) =(17+d)^2-25.
$$
