∑_(r=1)^n▒2/r(r+1)(r+2)
∑_(r=1)^n▒r/((2r-1)(2r+1)(2r+3))
I first convert both to partial fraction.
Then i use the method of differences to cancel off term by term, but i don't what term should i cancel.
Guide me through these two questions, please. Thank you.