Optimize an open-top box
Cut squares of side x from a 20 cm by 12 cm sheet. Volume V(x)=x(20-2x)(12-2x), with 0<x<6. Solving V'(x)=12x^2-128x+240=0 gives critical points x about 2.43 and x about 8.24.
- Respect the physical domain.
- Only one critical point is feasible.
- Endpoints give zero volume.