问题描述: 已知xy的值满足x+1/2=y+3/4=x+y/5,求代数式3x+2y+1/x+2y+3的值是多少 1个回答 分类:数学 2014-11-23 问题解答: 我来补答 已知(x+1)/2=(y+3)/4=(x+y)/5,得出,(x+1)/2=(y+3)/4 (2x+2)/4=(y+3)/4 则,2x+2=y+3 2x-y=1 .(1) 再将已知条件进行通分,(x+1)/2=(y+3)/4=(x+y)/5 (10x+10)/20=(5y+15)/20=(4x+4y)/20 得出,(10x+10)+(5y+15)=2*(4x+4y) 10x+5y+25=8x+8y 2x-3y=-25 .(2) (1)-(2)得出,2y=26,y=13 代入(1)得出,x=(y+1)/2=(13+1)/2=7 将x=7,y=13代入(3x+2y+1)/(x+2y+3) (3x+2y+1)/(x+2y+3) =(3*7+2*13+1)/(7+2*13+3) =48/36 =4/3 展开全文阅读