You can put this solution on YOUR website! Notice how you add seven each time and you also change the sign of each term?
You use that info to write your sum...you also need to figure how many terms there are...you can do that by seeing how any seven you need to go from 25 to 130...takes 15 more sevens...so we have...
25-32+39-46+53-.....-130 = from n = 1 to 15 of
