| I don't have the book right with me here, so I can't do the middle one.
23. Draw it out, and it is pretty easy to see the answer. If you have one line, it divides the plane into 2 (1 piece on each side of the line). If you have 2 lines, it divides the plane in 4. Think of a pie. If you add in a 3rd line, it divides two of those 4 sections (from before) into 2, thus adding 2 more. The answer is 6. |