## Intermediate Algebra for College Students (7th Edition)

$(2x^n+5y^m)^2$
The square of a binomial sum is: $(A+B)^2=A^2+2AB+B^2$. Hence here: $4x^{2n}+20x^ny^m+25y^{2m}=(2x^n)^2+2\cdot2x^n\cdot5y^m+(5y^m)^2=(2x^n+5y^m)^2$