I had a questions while watching the telescophic series part of the video. 

while you explain the pattern that exists within some type of telescophic series, I do not see how I determine what gets to be the first term (the one where you apply 1, 2, 3... to) and the last term (where you apply n-2, n-1, n.. to). 

I have a picture attached, I do not know if it will send correctly, but here is my best at explaining it in words. 

what is the difference between (1/(k+2)(k+5)) and (1/(k+5)(k+2))? because, to my understanding, if you put both in a sigma, they will result in a different result, since the first one (1/(k+2)(k+5)) has 1/(k+2) as its first term. so, on the final solution, the 1, 2, 3.. will be put into 1/(k+2). however, on the second one, (1/(k+5)(k+2)), the first term on paper is 1/(k+5). so, by putting in 1, 2, 3..., the final result will be different.