4x方-4xy+y方-4x+2y-15
=(2x-y)^2-2(2x-y)-15
=(2x-y-5)*(2x-y+3)
4x方y方-5x方y方-9y方 题目弄错了吧,应该是这样的吧
=4x^2y^2-5xy-9y^2
=(4x-9y)*(x+y)