a/ $9x^3y^2-15x^2y^3\\=3x^2y^2(3x-5y)$
Vậy $9x^3y^2-15x^2y^3=3x^2y^2(3x-5y)$
b/ $25x^2-49y^2\\=(5x)^2-(7y)^2\\=(5x-7y)(5x+7y)$
Vậy $25x^2-49y^2=(5x-7y)(5x+7y)$
c/ $x^2y-xy^2-7x+7y\\=(x^2y-xy^2)-(7x-7y)\\=xy(x-y)-7(x-y)\\=(xy-7)(x-y)$
Vậy $x^2y-xy^2-7x+7y=(xy-7)(x-y)$