xy+x+y=-13
xy=-13-(x+y)
x²+y²
=(x+y)²-2xy
=(x+y)²-2[-13-(x+y)]
=(x+y)²+26+2(x+y)=29
(x+y)²+2(x+y)-3=0
(x+y+3)(x+y-1)=0
1:x+y=-3
xy=-10
解得：x=-5 y=2或者x=2 y=5
2:x+y=1
xy=-14
解得：
解得:x=(1+√57)/2 y=(1-√57)/2 或者x=(1-√57)/2 y=(1+√57)/2