Answer
$(6a+5)^2$
Work Step by Step
The two numbers whose product is $ac=
36(25)=900
$ and whose sum is $b=
60
$ are $\{
30,30
\}$. Using these two numbers to decompose the middle term of the expression, $
36a^2+60a+25
,$ then the factored form is
\begin{array}{l}\require{cancel}
36a^2+30a+30a+25
\\\\=
(36a^2+30a)+(30a+25)
\\\\=
6a(6a+5)+5(6a+5)
\\\\=
(6a+5)(6a+5)
\\\\=
(6a+5)^2
.\end{array}
