Answer
$(2x^n+5y^m)^2$
Work Step by Step
The square of a binomial sum is: $(A+B)^2=A^2+2AB+B^2$.
Hence here: $4x^{2n}+20x^ny^m+25y^{2m}=(2x^n)^2+2\cdot2x^n\cdot5y^m+(5y^m)^2=(2x^n+5y^m)^2$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.