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(1) [(-1/3)x²y][(3/4)y²-(1/2)x+(1/3)]

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(1) [(-1/3)x²y][(3/4)y²-(1/2)x+(1/3)]
(2) 12x²y[(-2/3)x²-(5/6)xy+(3/4)y²]
(3) (4x²-y²)[(2x+y)²-(2x-y)²]
注:“/”是分数线,1/2是二分之一
(1) [(-1/3)x²y][(3/4)y²-(1/2)x+(1/3)]
(1)= (-1/4)x2y3+1/6x3y -1/9x2y (2)=(-8)x4y -10x3y2 +9x2y3 (3)=(4x2-y2)(2x+y+2x-y)(2x+y-2x+y) = (4x2-y2)8xy =32x3y -8xy3 注;x2 意思是x的平方