问题
解答题
已知直线l1:x+my+6=0,l2:(m-2)x+3y+2m=0,求m的值,使得:(1)l1⊥l2;(2)l1∥l2;(3)l1∩l2.
答案
(1)∵直线l1:x+my+6=0,l2:(m-2)x+3y+2m=0,由l1⊥l2 ,可得 1×(m-2)+m×3=0,解得m=
.1 2
(2)由l1∥l2 可得
=m-2 1
≠3 m
,解得 m=-1.2m 8
(3)由l1∩l2,可得1×3-(m-2)×m≠0,∴m≠-1且m≠3.