Answer
$36a^{2}$ - 12ab + $b^{2}$
This is a perfect square trinomial.
$36a^{2}$ - 12ab + $b^{2}$ = $(6a - b)^{2}$
Work Step by Step
$36a^{2}$ - 12ab + $b^{2}$
Notice that both the first and last terms are perfect squares:
$36a^{2}$ = 6a $\times$ 6a or = -6a $\times$ -6a
and $b^{2}$ = b $\times$ b or = -b $\times$ -b.
Also the middle term is -12ab = $2$ $\times$ $-6a$ $\times$ b.
Thus this is a perfect square trinomial:
$36a^{2}$ - 12ab + $b^{2}$ = $(6a)^{2}$ + 2(6a)(-b) + $(-b)^{2}$ = $(6a - b)^{2}$.