a: Ta có: \(x^2+2xy+y^2-4x^2y^2\)
\(=\left(x+y\right)^2-4x^2y^2\)
\(=\left(x+y+2xy\right)\left(x+y-2xy\right)\)
b: Ta có: \(x^6-y^6\)
\(=\left(x^3-y^3\right)\left(x^3+y^3\right)\)
\(=\left(x-y\right)\left(x+y\right)\left(x^2-xy+y^2\right)\left(x^2+xy+y^2\right)\)
c: Ta có: \(25-a^2+2ab-b^2\)
\(=25-\left(a-b\right)^2\)
\(=\left(5-a+b\right)\left(5+a-b\right)\)