当Y=0时
x²+(k+5)x+2k+6=0
x²+(k+5)x+[(k+5)/2] ²-[(k+5)] ²+2k+6=0
[x+(k+5)/2] ²=[(k+5)/2] ²-2k-6
[x+(k+5)/2] ²=(k²+10k+25)/4-2k-6
[x+(k+5)/2] ²=(k²+10k+25-8k-24)/4
[x+(k+5)/2] ²=(k²+2k+1)/4
[x+(k+5)/2] ²=[(k+1)/2] ²
X+(k+5)/2=±(k+1)/2
当X+(k+5)/2= (k+1)/2
X1=-2
当X+(k+5)/2=- (k+1)/2
X2=-k-3
因OA=2OB
则有两种情况
第一种
-2=2(-K-3)
K=-2
X2=-1
因A在B左侧,则坐标A(-2,0)、B(-1,0)
第二种
-4=-K-3
K=1
X2=-4
因A在B左侧,则坐标A(-4,0)、B(-2,0)