已知x+1/2=y+3/4=x+y/5,求式子3x+2y+1/2x-y+3
问题描述：
已知x+1/2=y+3/4=x+y/5,求式子3x+2y+1/2x-y+3
答
已知(x+1)/2=(y+3)/4=(x+y)/5,求式子(3x+2y+1)/(2x-y+3)
由题意得
(x+1)/2=(y+3)/4 ①
(x+1)/2=(x+y)/5 ②
由①得y=2x-1,代入②,得
(x+1)/2=(x+2x-1)/5
解得 x=7,
代入y=2x-1,
解得 y=13
∴(3x+2y+1)/(2x-y+3)
=(21+26+1)/(14-13+3)
=48/4
=12