Question 157330
Let {{{s}}}= original side
{{{s+5}}}= lengthened by 5 cm
{{{A[new]=81cm^2}}}
So, {{{A[new]=(s+5)^2}}} ---------------> working eqn
{{{81=s^2+10s+25}}}
{{{s^2+10s+25-81=0}}}
{{{s^2+10s-56=0}}}, factor out, perfect square
{{{(s+14)(s-4)=0}}}
2  values: {{{s=-14}}} ----------> don't use
{{{s=4cm}}} ---------------------> original side
In doubt? go back working eqn,
{{{81=(s+5)^2}}}
{{{81=(4+5)^2}}}
{{{81=9^2}}}
{{{81=81}}}
thank you,
Jojo