Question

下列直线中,与直线x-y-1=0垂直的是(    )

A.3x+y+1=0                          B.3x-y-1=0

C.x+3y+6=0                          D.x-3y-6=0

Answer 1

解析：∵直线3x-y-1=0的斜率k₁=,直线3x+3y+6=0的斜率k₂=-,

∴k₁·k₂=-1,

即与直线x-y-1=0垂直的是x+3y+6=0.

故选C.

答案：C