# How do you factor 16x^2 + 40xy + 25y^2 ?

It is ${\left(4 x + 5 y\right)}^{2}$
$16 {x}^{2} + 40 x y + 25 {y}^{2} = {\left(4 x\right)}^{2} + 2 \cdot 4 x \cdot 5 y + {\left(5 y\right)}^{2} = {\left(4 x + 5 y\right)}^{2}$