[(y-2x)(-2x-y)-4(x-2y)的2次方]乘(3y)ˇ2 半个中括号?=[(2x)²-y²-4(x²-4xy+4y²)]×(9x²)=(4x²-y²-4x²+16xy-16y²)×(9x²)=(16xy-17y²)×(9x²)=144x
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