Answer
$(2xy+7)^{2}$
Work Step by Step
Test whether this is a perfect square, $(A+B)^{2}=A^{2}+2AB+B^{2}$
First term: $A^{2}=(2xy)^{2}\Rightarrow A=2xy$
Third term: $B^{2}=(7)^{2}\Rightarrow B=7$
Test:$\qquad$ does $2AB$ equal the middle term?
$ 2AB=2(2xy)(7)=28xy\qquad$ ... yes, it does.
$\Rightarrow$This is a perfect square, $(2xy+7)^{2}$
