給定雙曲線x^2-y^2/2=1,過點A(2,1)的直線l與所給雙曲線交於P1,P2兩點,求線段P1P2中點P的軌跡方程

給定雙曲線x^2-y^2/2=1,過點A(2,1)的直線l與所給雙曲線交於P1,P2兩點,求線段P1P2中點P的軌跡方程

用點差法設直線方程為y-1=k(x-2),P1,P2為(x1,y1),(x2,y2),中點座標為((x1+x2)/2,(y1+y2)/2)將兩點座標分別代入方程,兩式再相减得:(x1-x2)*(x1+x2)=0.5*(y1-y2)*(y1+y2)(y1-y2)/(x1-x2)=2*(x1+x2)/(y1+y2)…