Question

若直線y=kx與圓(x-2)²+y²=1的兩個交點關于直線2x+y+b=0對稱,則k,b的值分別為(　　)

A.k=,b=-4          B.k=-,b=4

C.k=,b=4               D.k=-,b=-4

Answer 1

A.因為直線y=kx與圓(x-2)²+y²=1的兩個交點關于直線2x+y+b=0對稱,則y=kx與直線2x+y+b=0垂直,且2x+y+b=0過圓心,所以解得k=,b=-4.