The question is in the description

Question

 A poster is to have a total area of 776 square inches with top and bottom margins of 3 inches and side margins of 2 inches (you cannot print on the margins). What should be the dimensions of the poster so that the printed area is as large as possible?

Answer 1

LW=776 => W=776/L

A = (L-6)[(776/L)-4] = 776-4L-(6*776/L)+24

dA/dL = -4 + 6*776/L² = 0

L² = 3*388

L=34.11744

W=22.74903

I always hate it when problems like this come out with "ugly" answers ...but I think this is correct.