zhaoyt1981
幼苗
共回答了18个问题采纳率:83.3% 举报
由直线kx-y+
2 =0与圆x 2 +y 2 =4相交于A,B两点,联立两方程得:(1+k 2 )x 2 +2
2 kx-2=0
∴x A +x B =-
2
2 k
1+ k 2 ,y A +y B =kx A +
2 +kx B +
2 =
2
2
1+ k 2
∵
OM =
OA +
OB ,
∴M(-
2
2 k
1+ k 2 ,
2
2
1+ k 2 )
代入圆x 2 +y 2 =4可得 (-
2
2 k
1+ k 2 ) 2 +(
2
2
1+ k 2 ) 2 =4
∴k=±1
故答案为:±1
1年前
9