1. Find the points on the curve $\displaystyle 9x^2 + 4xy + 6y^2 = 11$ that are farthest away from the origin.

I'm totally lost on this one.

and the second question:

Let $\displaystyle g(x) = 2x^5 - 10x^3 + 15x - 3$ . Find the intervals on which g is increasing or decreasing.

after finding $\displaystyle g'(x)=10x^4-30x^2+15$, what is the next step??(Thinking)