X分之1加Y分之1＝2,则2X减XY加2Y除以3X加5XY加3Y＝?一道数学题很简单的考考你们 步骤也要

1/x+1/y=2
得(x+y)/xy=2,xy=(2+y)/2
(2x-xy+2y)/(3x+5xy+3y)=[2(x+y)-(2+y)/2]/[3(x+y)+2.5(x+y)]
=(2-0.5)/(3+2.5)
=3/11

原式上下同时除以xy原式化为[2(1/X+1/Y)-1]/[3(1/x+1/y)+5]
因为X分之1加Y分之1＝2,所以原式=(4-1)/(6+5)=3/11

可以告诉楼主一个简单的算法用特殊值法，很明显可以得出一组解x=y=1，代入所求式
（2-1+2）/（3+5+3）=3/11

(1/x)+(1/y)=2
通分得
(x+y)/(xy)=2
x+y=2xy
(2x-xy+2y)/(3x+5xy+3y)
=[2(x+y)-xy]/[3(x+y)+5xy]
=(2×2xy-xy)/(3×2xy+5xy)
=(3xy)/(11xy)
=3/11

1/x+1/y=2
(x+y)/xy=2
x+y=2xy
(2x-xy+2y)/(3x+5xy+3y)
=[2(x+y)-xy]/[3(x+y)+5xy]
=(4xy-xy)/(6xy+5xy)
=3xy/11xy
=3/11