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2014-05-26T23:49:13-03:00
9^2=81 9+81=90 Espero ter ajudado
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  • Usuário do Brainly
2014-05-27T00:13:13-03:00
x+x^2 = 90
x^2 + x - 90 = 0

Formula Bhaskara

 \frac{-b +-  \sqrt{b^{2} -4.a.c } }{2.a}    ⇒  \frac{-1 +-  \sqrt{1^{2} -4.1.-19 } }{2.1}

\frac{-1 +- \sqrt{1 +  360 } }{2} ⇒  \frac{-1 +- 19 }{2}

\frac{-1 - 19 }{2} =  \frac{-20}{2} = -10

\frac{-1 + 19 }{2} =  \frac{18}{2} = 9

 
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Note que
-10 + 100 = 90
81+9 = 90