Question

经过圆x²+2x+y²=0的圆心C,且与直线x+y=0垂直的直线方程是(    )

A.x+y+1=0                         B.x+y-1=0

C.x-y+1=0                          D.x-y-1=0

Answer 1

答案：C  x-y+1=0  x²+2x+y²=0化为(x+1)²+y²=1,

∴圆心(-1,0).

与直线x+y=0垂直的直线斜率为1,

∴所求的方程为y=x+1.