1 配方得 (x-1)²+(y-2)²=-m+5 -m+5>0 m<52 带入方程 (4-2y-1)²+(y-2)²=-m+5 5y²-16y+8+m=0 设 M(4-2y1,y1) N(4-2y2,y2) om斜率为y1/(4-2y1) on斜率 y2/(4-2y2) 所以y1/(4-2y1)*y2/(4-2y2)=-1 y1+y2=16/5 y1*y2=(8+m)/5带入求出m