4x^2y-9y^3+2x-3y
=(2x+3y)(2x-3y)y+(2x-3y)
=(2x-3y)[(2x+3y)y+1]
=(2x-3y)(2xy+3y²+1)(x+y)^2+7(x+y)+12 因式分解(x+y)^2+7(x+y)+12=[(x+y)+3][(x+y)+4]=(x+y+3)(x+y+4)