x^2-4y^2+2x-4y

问题描述:

x^2-4y^2+2x-4y

x^2-4y^2+2x-4y
=(x^2+2x+1)-(4y^2+4y+1)
=(x+1)^2-(2y+1)^2
=(x+1+2y+1)(x+1-2y-1)
=(x+2y+2)(x-2y)