解方程组 x2+y2=10 x+xy+y=7

2024-12-19 00:58:22
推荐回答(3个)
回答1:

∵x^2+y^2=10,x+xy+y=7
∴ 7-xy=x+y,且2xy≤x^2+y^2=10,
∴(7-xy)^2=(x+y)^2=x^2+y^2+2xy=10+2xy,且xy≤5
∴49-14xy+(xy)^2=10+2xy,即(xy)^2-16xy+39=0,解得xy=3或xy=13(舍去)
∴x=3/y,代入x^2+y^2=10并整理得y^4-10y^2+9=0,解得y=1或y=-1或y=3或y=-3
∴当y=1时,x=3,当y=-1时,x=-3,当y=3时,x=1,当y=-3时,x=-1

回答2:

(1,3)

回答3:

x=3 y=1或x=1 y=3