Answer
$40xy$
Work Step by Step
The square of a binomial sum is: $(A+B)^2=A^2+2AB+B^2$.
The square of a binomial difference is: $(A-B)^2=A^2-2AB+B^2$.
Hence here: $(5x+2y)^2-(5x-2y)^2=(5x^2)+2\cdot5x\cdot2y+(2y)^2-[(5x^2)-2\cdot5x\cdot2y+(2y)^2]=20xy-(-20xy)=40xy$
