16﹙x+y﹚²-25﹙x-y﹚²
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16﹙x+y﹚²-25﹙x-y﹚²16﹙x+y﹚²-25﹙x-y﹚²16﹙x+y﹚²-25﹙x-y﹚²=[4(x+y)]²-[5(
16﹙x+y﹚²-25﹙x-y﹚²
16﹙x+y﹚²-25﹙x-y﹚²
16﹙x+y﹚²-25﹙x-y﹚²
=[4(x+y)]²-[5(x-y)]²
=[4(x+y)+5(x-y)][4(x+y)-5(x-y)]
=(9x-y)(-x+9y)
=-(9x-y)(x-9y)
计算：=-9x²+82xy-9y²
16﹙x+y﹚²-25﹙x-y﹚²
=[4(x+y)+5﹙x-y﹚][4(x+y)-5﹙x-y﹚]
=(4x+4y+5x-5y)(4x+4y-5x+5y)
=(9x-y)(9y-x)