若xy/(x+y)=3,则(6x+4xy+6y)/(9x+4xy+9y)=______

来源：学生作业学帮网编辑：学帮网时间：2024/05/16 19:18:17

XY/（X+Y）=3,XY=3（X+Y）
原式=［6（X+Y）+4XY］/［9（X+Y）+4XY］
=［6（X+Y）+12（X+Y）］/［9（X+Y）+12（X+Y）］
=［18（X+Y）］/［21（X+Y）］
=18/21
=6/7

xy/(x+y)=3可得xy＝3(x+y）
则原式(6x+4xy+6y)/(9x+4xy+9y)＝6xy/7xy＝6/7

6/7

显然xy=3(x+y)
替换所有的xy
=(6x+4*3(x+y)+6y)/(9x+4*3(x+y)+9y)
=[18(x+y)]/[21(x+y)]
=18/21
=6/7

xy/(x+y)=3 则xy=3(x+y) 代入得
(6x+4xy+6y)/(9x+4xy+9y)
=[18(x+y)]/[21(x+y)]
=18/21
=6/7

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