Question

Encontre as raízes das equações:
a) x² - X - 20 = 0​

Answer 1

Resposta:

x² - x - 20 = 0​

ax² + bx + c = 0

a = 1

b = - 1

c = - 20

Calcular o  Δ:

Δ = b² - 4* a *c

Δ = (-1)² - 4 * 1 *(-20)

Δ = 1 + 80

Δ = 81

$x = \dfrac{-b\pm\sqrt{\Delta}}{2a} = \dfrac{-(-1) \pm\sqrt{81}}{2\times 1} = \dfrac{1\pm\sqrt{81}}{2} = \dfrac{1\pm \,9}{2} \\\\\\x_1 = \dfrac{1 + 9}{2} =\dfrac{10}{2} = 5\\\\x_2 = \dfrac{1- 9}{2} = \dfrac{-\,8}{2} = - 4$