Question

calcule as raizes da equação a seguir
x²-×-20=0​

Answer 1

$\boxed{\begin{array}{lr} x^2-x-20=0 \end{array}}\\\boxed{\begin{array}{lr} a=1\\b=-1\\c=-20 \end{array}}\\\boxed{\begin{array}{lr} \Delta=b^2-4.a.c\\\Delta=(-1)^2-4.1.-20\\\Delta=1+80\\\Delta=81 \end{array}}\\\boxed{\begin{array}{lr} x=\dfrac{-b\pm\sqrt{\Delta}}{2.a}\\\\x=\dfrac{1\pm\sqrt{81}}{2.1}\\\\x=\dfrac{1\pm9}{2} \end{array}}\\\boxed{\begin{array}{lr} x'=\dfrac{1+9}{2} \ \ \ \ \ x'=\dfrac{10}{2} \ \ \ \ \ x'=5\\\\x''=\dfrac{1-9}{2} \ \ \ \ \ x''=\dfrac{-8}{2} \ \ \ \ \ x''=-4\end{array}}$

Resposta Correta;

$S=\{-4 \ \ , \ 5\}$

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