两边对x求导有 2x+y+xy'+2yy'=0, 把x=1,y=1代入有 2 + 1 + y' +2y'=0,得 y‘=-1 所以切线斜率为-1 所以切线方程为 y-1 = -(x-1) 整理有 y=-x+2,9, 将(1,1)代入x^2+xy+y^2=3成立, 则点(1,1)在曲线上 求导数2x+y+xy'+2yy'=0 y'=-(2x+y)/(x+2y)=-1 y-1=-(x-1) 所求的切线方程是x+y-2=0,1,