Question 1185597
From  {{{4*10}}} {{{ft^2}}}  to {{{(4+x)(10+x)=2*4*10}}}


{{{4*10+10x+4x+x^2=2*4*10}}}

{{{14x+x^2=4*10}}}

{{{x^2+14x=40}}}

{{{x^2+14x-40=0}}}

{{{x=(-14+- sqrt(196+4*40))/2}}}

{{{x=(-14+- sqrt(356))/2}}}

{{{x=-7+sqrt(89)}}}  {{{about}}}{{{2.434}}}


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check:  {{{(4+2.434)(10+2.434)=6.434*12.434=80.00}}}