数学问题已知实数x,y满足x^2+2xy
已知实数x,y满足x^2+2xy-1=0,求x+y的取值范围。
x^2+2xy-1=0 x^2+2xy+y^2-1-y^2=0 x^2+2xy+y^2=y^2+1>=1 (x+y)^2=y^2+1>=1 所以x+y>=1或x+y<=-1