Question

Resolva a equação do 2° grau utilizando a fórmula de Bhaskara
X3+X-90=0

Answer 1

Fórmula de Bhaskara: $x = \dfrac{-b\pm \sqrt{b^2-4ac}}{2a}$

Substituindo:

$x = \dfrac{-1\pm \sqrt{1^2 -4\cdot 1\cdot (-90)}}{2\cdot 1}$

$x = \dfrac{-1\pm \sqrt{1 + 360}}{2}$

$x = \dfrac{-1\pm 19}{2}$

$x_1 = \dfrac{-1 + 19}{2}$

$x_1 = \dfrac{18}{2}$

$x_1 = 9$

$x_2 = \dfrac{-1- 19}{2}$

$x_2 = \dfrac{-20}{2}$

$x_2 = -10$

$S = \left\{9,\, -10\right\}$

Alternativa C.