a) Ta có: \(x^2-2xy+y^2-2x+2y\)
\(=\left(x-y\right)^2-2\left(x-y\right)\)
\(=\left(x-y\right)\left(x-y-2\right)\)
b) Ta có: \(x^2-4x+4-x^2y+2xy\)
\(=\left(x-2\right)^2-xy\left(x-2\right)\)
\(=\left(x-2\right)\left(x-2-xy\right)\)
c) Ta có: \(ax^2-3axy-x^2+6xy-9y^2\)
\(=ax\left(x-3y\right)-\left(x^2-6xy+9y^2\right)\)
\(=ax\left(x-3y\right)-\left(x-3y\right)^2\)
\(=\left(x-3y\right)\left(ax-x+3y\right)\)
d) Ta có: \(2a^2x-5a^2y-4x^2+30xy-25y^2\)
\(=a^2\left(2x-5y\right)-\left(4x^2-30xy+25y^2\right)\)
\(=a^2\left(2x-5y\right)-\left(2x-5y\right)^2\)
\(=\left(2x-5y\right)\left(a^2-2x+5y\right)\)