Question

Calcular As Raizes das Equações Abaixo:


a) x2- x- 20= 0

Answer 1

x² - x - 20 = 0

a = 1
b = -1
c = -20

Δ = b² -4 . a.  c
Δ = (-1)² -4 . 1 . (-20)
Δ = 1 + 80
Δ = 81

$\mathtt{\dfrac{-b+-~\sqrt{\Delta}}{2~.~a}~~=~~\dfrac{-(-1)+-~\sqrt{81}}{2~.~1}~~=~~\dfrac{1+-~9}{2}} \\ \\ \\ \mathtt{x' =\dfrac{1 + 9}{2}~~=~~\dfrac{10}{2}~~=~~5} \\ \\ \\ \mathtt{x'' = \dfrac{1-9}{2}~~=~~-\dfrac{8}{2}~~=~~-4} \\ \\ \\ \boxed{\boxed{\mathtt{Resposta: S:~~ -4~~~e~~ 5}}}$