已知双曲线3x^2-y^2=3,求以定点A（2,1）为中点的弦所在的直线方程

点差法设M(X1,y1).N(x2,y2),为直线与双曲线的交点,将点坐标代入曲线方程,得3x1^2-y1^2=33x2^2-y2^2=3两式相减得3（x1^2-x2^2)=y1^2-y2^2变形得（y1-y2)/(x1-x2)=3(x1+x2）/（y1+y2),式子左边即直线斜率,右边用中点坐...