Question 1077768
Original square is side x.


Area of original square, {{{x^2}}}.


The changed figure:
{{{(x+6)(x+3)=3x^2}}}



Finding x.
{{{3x^2=x^2+9x+18}}}
{{{2x^2=9x+18}}}
{{{2x^2-9x-18=0}}}
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discrim, {{{81+4*2*18=225=15^2}}}
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{{{x=(9+15)/4}}}
{{{highlight(x=6)}}}