Max U
Case:

If you’re unsure about the basic rules of differentiation, see this handout:
 Differentiation, January 2013
If you’re unsure about using the Lagrangian method, here’s a video overview:
Another good example is here:
Learning Objectives: Analyse alternative indifference curves. Solve a Lagrangian maximisation
Focus on diversity: Joan’s utility function is named after the famous economist Joan Robinson 