Question

Assinale a alternativa correta, da qual indica as raízes da Equado Quadrática
a) ײ-×-20=0

• (4,-5)
• (5,4)
• (1,-20)
• (5,-4)
• (-1,-20)


b) 12+4×-ײ=0

(6,-2)
(6,2)
(12,4)
(-12,4)
(12,-1)​

Answer 1

Por Bháskara:

a) $\frac{-(-1)+-\sqrt{(-1)^{2} -4.1.(-20) } }{2.1} </p><p>\\\\\\frac{1+-\sqrt{81} }{2} </p><p>\\\\\\Observe que \sqrt{81} =9</p><p>\\\\\\Logo, \frac{1+9}{2} = \frac{10}{2} = 5</p><p>\\\frac{1-9}{2} =\frac{-8}{2} =-4$$\frac{-(4)+-\sqrt{(4)^{2} -4.(-1).12 } }{2.(-1)} \\\\\frac{-4+-\sqrt{64} }{-2}\\ Note que \sqrt{64} = 8</p><p>\\\\frac{-4+8}{-2} = \frac{4}{-2} = -2\\\\\frac{-4-8}{-2} = \frac{-12}{-2} = 6$

Portanto, as raízes são: (5,-4)

b)  Note que organizando a ordem: -x^2+4x+12

$\frac{-4+- \sqrt{(4)^{2} -4.-1.12 } }{2.-1} \\\frac{-4+-\sqrt{64} }{-2} \\Note que \sqrt{64} = 8\\ \\Portanto, \frac{-4+8}{-2} = \frac{4}{-2} =-2\\e\\\frac{-4-8}{-2} = \frac{-12}{-2} = 6$

Portanto, as raízes são: (6,-2)