Question

8) As raizes da equação x2 +3x-28= 0 são:
(A) -2 e 10
(B) 3 e-11
(C) 0 e 2
(D) 4 e -7​

Answer 1

Explicação passo-a-passo:

$\sf x^2 + 3x - 28 = 0$

coeficientes: a = 1, b = 3, c = - 28

$\sf \Delta = b^2 - 4ac$

$\sf \Delta = (3)^2 - 4*(1)*(-28)$

$\sf \Delta = 9 + 112$

$\sf \Delta = 121$

$\sf x = \dfrac{- b \pm \sqrt{\Delta}}{2a}$

$\sf x = \dfrac{- (3) \pm \sqrt{121}}{2*(1)}~\Rightarrow~x = \dfrac{- 3 \pm 11}{2}$

$\sf x' = \dfrac{- 3 + 11}{2}~\Rightarrow~x' = \dfrac{8}{2}~\Rightarrow~x' = \red{4}$

$\sf x'' = \dfrac{- 3 - 11}{2}~\Rightarrow~x'' = - \dfrac{14}{2}~\Rightarrow~x'' = \red{- 7}$

Raizes: 4 e - 7

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