化简求值(X-y)(x-2y)+(X-2Y)(X-3Y)-2(X-3Y)(X-4Y),其中=4 Y=2|3(二分之三)
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(X-y)(x-2y)+(X-2Y)(X-3Y)-2(X-3Y)(X-4Y)
=(x-2y)(x-y+x-3y)-2(x-3y)(x+4y)
=(x-2y)(2x-4y)-2(x-3y)(x+4y)
=2x²-4xy-4xy+8y²-2x²-16xy+6xy+24y²
=-18xy+32y²
=-18x4x3/2+32x(3/2)²
=-108+207
=99
=(x-2y)(x-y+x-3y)-2(x-3y)(x+4y)
=(x-2y)(2x-4y)-2(x-3y)(x+4y)
=2x²-4xy-4xy+8y²-2x²-16xy+6xy+24y²
=-18xy+32y²
=-18x4x3/2+32x(3/2)²
=-108+207
=99
追问
书上答案是0，你说的不对
追答
(X-y)(x-2y)+(X-2Y)(X-3Y)-2(X-3Y)(X-4Y)
=(x-2y)(x-y+x-3y)-2(x-3y)(x-4y)
=(x-2y)(2x-4y)-2(x-3y)(x-4y)
=2x²-4xy-4xy+8y²-2(x²-4xy-3xy+12y²)
=2x²-4xy-4xy+8y²-2x²+8xy+6xy-24y²
=6xy-16y²
=6x4x3/2-16x(3/2)²
=36-36
=0
祝学习进步，望采纳~~
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