Could someone explain something about this question?
http://gyazo.com/cba3450ed278963ff227112c0f8b937aSo when changing the limits the first time round for part C, I expanded the substitution and set it equal to 5, and then to 2 which gave me upper limits of both 6 and 2 and lower limits of 3 and 5.
However, realising I had made a mistake, I just substituted 5 and then 2 into the original substitution and got limits of 6 and 5 only.
Can anyone tell me why I eliminated the 2 and 3 the second time round? I know it has something to do with the positive square root but I don't really understand it. Thanks