9(x-y)的平方减16(x+y)的平方等于多少

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9(x-y)的平方减16(x+y)的平方等于多少

9(x-y)的平方减16(x+y)的平方等于多少
9(x-y)的平方减16(x+y)的平方等于多少

9(x-y)的平方减16(x+y)的平方等于多少
=[3x-3y+4x+4y][3x-3y-4x-4y]
=(7x+y)(-x-7y)
=-(7x+y)(x+7y)

...=[3(x-y)+4(x+y)]*[3(x-y)-4(x+y)]=(7x+y)*(-x-7y)=-(7x+y)*(x+7y)=-7x^2-50xy-7y^2

9(x-y)²-16(x+y)²
=9x²-18xy+9y²-16x²-16y²-32xy
=-7x²-7y²-50xy
= ﹣(7x+y)(x+7y)

9(x-y)^2-16(x+y)^2答案应该是-7(x^2+y^2)-50xy