Answer
$(4p-5)^{2}$
Work Step by Step
Test whether this a perfect square, $(A-B)^{2}=A^{2}-2AB+B^{2}$
First term: $A^{2}=(4p)^{2}\Rightarrow A=4p$
Third term: $B^{2}=5^{2}\Rightarrow B=5$
Test: does $-2AB$ equal the middle term?
$-2AB=-2(4p)(5)=-40p\qquad$ ... yes, it does.
This is a perfect square,
$16p^{2}-40p+25=A^{2}-2AB+B^{2}=(A-B)^{2}$
$(A-B)^{2}=(4p-5)^{2}$
