9(x+y)²-(x－y)²

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9(x+y)²-(x－y)²9(x+y)²-(x－y)²9(x+y)²-(x－y)²9(x+y)²-(x-y)²=[3(

9(x+y)²-(x－y)²
9(x+y)²-(x－y)²

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

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