Question

用换元法解方程组 13/x+1 +7/y+1=9 6/x+1+7/2(y+1)=5

Answer 1

令a=1/(x+1),b=1/(y+1)

所以13a+7b=9 (1)

6a+7b/2=5 (2)

(1)-(2)×2

a=-1

b=22/7

1/(x+1)=-1

x+1=-1

x=-2

1/(y+1)=22/7

y+1=7/22

y=-15/22

所以x=-2,y=-15/22