Answer
$s=-10$.
Work Step by Step
The given polynomial is
$\Rightarrow s^2+20s+100=0$
Write the the polynomial as $a^2+2ab+b^2$.
$\Rightarrow s^2+2(s)(10)+10^2=0$.
Use perfect square trinomial pattern
$a^2+2ab+b^2=(a+b)^2$.
We have $a=s$ and $b=10$.
$\Rightarrow (s+10)^2=0$.
Use zero product property.
$\Rightarrow s+10=0$.
Solve for $s$.
$\Rightarrow s=-10$.
Hence, the solution is $s=-10$.