Hi

i am having trouble getting the correct answer on the following question:

A box open at the top has a volume of . Find the dimensions which give minimum surface area.

(1)

(2)

sub w into (2) equation

(3)

(4)

make x the subject of equation (4)

sub back into equation (3)

therefore

or

0 is unrealistic so don't consider it.

my answer m , m, 16m

answer is cubic root 20m, cubic root 20m, 0.5 cubic root 20m

P.S