Question 1093825
What is the minimum amount of fencing needed to construct a rectangular enclosure containing 1800 square feet using a river as a natural boundary on one side? 
:
let L = the length
let w = the width
:
Area
L * w = 1800
L = {{{1800/w}}}
:
perimeter (p), only 3 sides of fence required, therefore
p = L + 2w
Replace L with {{{1800/w}}}
p(w) = {{{1800/w}}} + 2w 
:
Plot this equation 
{{{ graph( 300, 200, -50, 150, -50, 200, (1800/x)+2x, 120) }}} 
minimum fencing occurs when w = 30, then L = 1800/60 = 60
therefore min fencing is 120 (green line). 60 + 2(30)