Question 950339
For a rectangle,
{{{A=L*W=160}}}
{{{(W+4)W=160}}}
{{{W^2+4W=160}}}
{{{W^2+4W+4=160+4}}}
{{{(W+2)^2=164}}}
{{{W+2=0 +- sqrt(164)}}}
{{{W=-2 +- 2sqrt(41)}}}
Since we're only interested in the positive solution,
{{{W=-2+2sqrt(41)}}} 
So then,
{{{L=-2+2sqrt(41)+4}}}
{{{L=2+2sqrt(41)}}}