∴: Are these three points on the same straight line?

2.l equation: y=k(x+ 1)+2.

①: When l intersects with point A (-2, -3), then: -3=-k+2 to get k=5.

②: When L intersects with point B (3,0), then: 0=4k+2, and k=- 1/2.

∴ k∈[5，∞]∨[-∞，- 1/2]

3. When L 1 and L2 are perpendicular to the line segment AB, the maximum distance from L 1 to L2 is |AB|.

At this time, the slopes of L 1 and L2 are equal, which are-1/k(AB)=- 1/3 respectively.