4\(x+y)+5\(x-y)=3
4\(x+y)-5\(x-y)=-1
设4/(x+y)=s,5/(x-y)=t,
原方程组成为,
s+t=3,
s-t=-1
解得
s=1,
t=2
所以
4/(x+y)=1,
5/(x-y)=2,
x+y=4,
x-y=2.5,
解得x=3.25
y=0.75题目错误，你的方法也不是我想要的