Question 1130087
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The correct answer is  x= {{{-10 + 10*sqrt(2)}}}.


<U>Check</U>.  x^2 + 20x = {{{(-10+10*sqrt(2))^2 + 20*(-10+10*sqrt(2))}}} = {{{100 - 200*sqrt(2) + 200 + -200 + 200*sqrt(2))}}} = {{{100}}}.   ! Correct !
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