(x+2y)^4-3(x^2-4y^2)^4-18(2y-x)^4

来源：学生作业帮编辑：百度作业网作业帮分类：数学作业时间：2024/08/15 22:11:32

题目错了：第二个括号的指数是2,不是4
原式=[(x+2y)²]²-3(x+2y)²*(x-2y)²-18[(x-2y)²]²
=[(x+2y)²-6(x-2y)²][(x+2y)²+3(x-2y)²]
=(x²+4xy+4y²-6x²+24xy-24y²)(x²+4xy+4y²+3x²-12xy+12y²)
=(-5x²+28xy--20y²)(4x²-8xy+16y²)
=-4(5x²-28xy+20y²)(x²-2xy+4y²)
再问：就是4好吧！卷子上就是这样的！！！

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