Question

${x}^{2} - 5x + 8 = 0$
mim ajudem nessa equação de 2° gral? ​

Answer 1

    $x^2-5x+8=0$

    $x=\frac{-(-5)\pm\sqrt{(-5)^2-4\times1\times8}}{2\times1}\Leftrightarrow$

$\Leftrightarrow x=\frac{5\pm\sqrt{25-4\times8}}{2}\Leftrightarrow$

$\Leftrightarrow x=\frac{5\pm\sqrt{25-32}}{2}\Leftrightarrow$

$\Leftrightarrow x=\frac{5\pm\sqrt{-7}}{2}$   (Impossível)

Logo,  $x\in\{\;\;\}$