Answer
A perfect square trinomial is a result of expanding an expression which is a square of a sum of terms, or a square of a difference of terms.
The perfect squre trinomial is recognizable by having
two $(+)$squares and a $(\pm)$double product:
$A^{2}+2AB+B^{2}=(A+B)^{2},$
$A^{2}-2AB+B^{2}=(A-B)^{2}$
Work Step by Step
The question asks for an explanation; there are no steps.