设1/x+y=t 1/x-y=v
则3t+2v=17/5 2t-5v=1
6t+4v=34/5 6t-15v=3
19v=19/5
v=1/5
t=1
1/x+y=1 1/x-y=1/5
x+y=1 x-y=5
x=3 y=-2