I really don't understand calculus and limits... everything seems pointless, i mean why are we doing the things we do here?? What's the point of dividing the whole expression by the highest power of n? When do we use that?
Also i have a picture here of two different exercises which i totally don't understand.. in the first exercise he removes the square roots from the numerator, in the second he removes it from the denominator. What's the point of this??
I made an image for you to better see the problem:
$ \lim \frac{\sqrt{(n^2)+n}-n}1 = \frac{\sqrt{(n^2)+n}-n}1 * \frac{\sqrt{(n^2)-n}+n}{\sqrt{(n^2)+n}+n} $
and
$ \lim \frac{1}{\sqrt{9n^2+5n}-3n} = \frac{1}{\sqrt{9n^2+5n}-3n}* \frac{\sqrt{9n^2+5n}+3n}{\sqrt{9n^2+5n}+3n} $