Im going over a solution to the following problem, and was stuck trying to figure out how to get the final answer. If i substitute (n-1)/2 for k i would get:

((n-1)/2)( ((n-1)/2 ) + 1) and not the final answer given in the solution given.

problem 28:

prove the following.

https://lh4.googleusercontent.com/_2...405_210358.jpg

the solution:

http://i52.tinypic.com/287kp3m.png