Math Help - Finding critical points

1. Finding critical points

Consider the function f(x,y)=x^2+y^2+2x^3/
a) Find and classify all critical points.
b) Find the absolute extrema on the disk x^2+y^2 <= 1 using Lagrange multipliers to do the boundary.

2. Hello,

Calculate $\frac{\partial f}{\partial x}$ and $\frac{\partial f}{\partial y}$

A critical point is a point where both $\frac{\partial f}{\partial x}$ and $\frac{\partial f}{\partial y}$ are equal to 0.

3. I was more concerned about part b