[(x²-y²)+(x²+y²)][(x²-y²)-(x²+y²)]

[(x²-y²)+(x²+y²)][(x²-y²)-(x²+y²)]
[(x²-y²)+(x²+y²)][(x²-y²)-(x²+y²)]

[(x²-y²)+(x²+y²)][(x²-y²)-(x²+y²)]
[(x²-y²)+(x²+y²)][(x²-y²)-(x²+y²)]
=(x²-y²+x²+y²)(x²-y²-x²-y²)
=(2x²)(-2y²)
=-4x²y²

前一个中括号打开得2X^2 后一个打开得﹣2Y^2所以乘起来得﹣4X^2Y^2

-4x²y²