2)Use chain rule
Then visually inspect and equate coefficients
3) Your best bet here is to just multiply through by 36, and then use implicit differentiation
You can decimate this one by noting that
5) This is an SDE (Seperable Differential Equation), seperate variables and integrate. If you have any problems report back
6) Here, you must just sketch it, and remember that
where || denotes absolute value
7) I am assuming that this is just the limit as x goes to zero?
For the approximation put in x=.00001 and x=-.00001
For the actual limit, I assume you do not know Maclaurin series, so I would suggest L'hopital's. Or a clever usage of algaebraic manipulation.
If you have any problems just post back