1.因式分解 4（x-y）²-9（x+y）²

1.因式分解 4（x-y）²-9（x+y）²

4（x-y）²-9（x+y）² 平方差
=[2(x-y)-3(x+y)][2(x-y)+3(x+y)]
=(2x-2y-3x-3y)(2x-2y+3x+3y)
=(-x-5y)(5x+y)
=-(x+5y)(5x+y)

原式=[2(x-y)]²-[3(x+y)]²
=[2(x-y)+3(x+y)][2(x-y)-3(x+y)]
=-(5x+y)(x+5y)

4（x-y）²-9（x+y）²
=[2(x-y)+3(x+y)[(2(x-y)-3(x+y)]
=(5x+y)(-x-5y)
=-(5x+y)(x+5y)

4(x-y)^2-9(x+y)^2=[2(x-y)]^2-[3(x+y)]^2
=[2(x-y)+3(x+y)][2(x-y)-3(x+y)]
=(5x+y)(-x-5y)
=-(x+5y)(5x+y)

-5(x²+Y²）-26xy