已知x/y=2/3求[5y^2/(x-2y)-x-2y]÷(x^2-6xy+9y^2)/(x-2y)的值
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已知x/y=2/3求[5y^2/(x-2y)-x-2y]÷(x^2-6xy+9y^2)/(x-2y)的值
x/y=2/3
所以y=3x/2
原式=[5y²-(x-2y)(x+2y)]/(x-2y)÷(x-3y)²/(x-2y)
=(9y²-x²)/(x-2y)*(x-2y)/(x-3y)²
=-(x+3y)(x-3y)/(x-2y)*(x-2y)/(x-3y)²
=-(x+3y)/(x-3y)
=-(x+3x/2)/(x-3x/2)
=5
再问: -(x+3x/2)/(x-3x/2)这一步的计算结果好像不是5啊
再答: 对
采纳吧
再问: =-(x+3y)/(x-3y)
=-(x+3x/2)/(x-3x/2)这两部是怎么转换过来的?不是3x/2还要乘以三吗
再答: 哦,对不起,是错了
x/y=2/3
所以y=3x/2
原式=[5y²-(x-2y)(x+2y)]/(x-2y)÷(x-3y)²/(x-2y)
=(9y²-x²)/(x-2y)*(x-2y)/(x-3y)²
=-(x+3y)(x-3y)/(x-2y)*(x-2y)/(x-3y)²
=-(x+3y)/(x-3y)
=-(x+9x/2)/(x-9x/2)
=11/7
所以y=3x/2
原式=[5y²-(x-2y)(x+2y)]/(x-2y)÷(x-3y)²/(x-2y)
=(9y²-x²)/(x-2y)*(x-2y)/(x-3y)²
=-(x+3y)(x-3y)/(x-2y)*(x-2y)/(x-3y)²
=-(x+3y)/(x-3y)
=-(x+3x/2)/(x-3x/2)
=5
再问: -(x+3x/2)/(x-3x/2)这一步的计算结果好像不是5啊
再答: 对
采纳吧
再问: =-(x+3y)/(x-3y)
=-(x+3x/2)/(x-3x/2)这两部是怎么转换过来的?不是3x/2还要乘以三吗
再答: 哦,对不起,是错了
x/y=2/3
所以y=3x/2
原式=[5y²-(x-2y)(x+2y)]/(x-2y)÷(x-3y)²/(x-2y)
=(9y²-x²)/(x-2y)*(x-2y)/(x-3y)²
=-(x+3y)(x-3y)/(x-2y)*(x-2y)/(x-3y)²
=-(x+3y)/(x-3y)
=-(x+9x/2)/(x-9x/2)
=11/7
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