Question 399245
A rectangular box with volume 18 cubic metres has a square base with side length x metres. 
Express the surface area S of the box as a function of x.
:
The Volume of box with a square base: V = x^2 * h
x^2 * h = 18
h = {{{h/x^2}}}
:
Surface area: S.A. = 2(L*W) + 2(L*h) + 2(W*h)
In this problem:
L & W = x; h = {{{18/x^2}}}
we have
S.A. = 2x^2 + 4(x*{{{18/x^2}}}) 
S.A. = 2x^2 + {{{72/x}}}