Question

Encontre as raízes ou zeros da função f(x) = x² – 4x – 5. ( Use formula de bhaskara). *



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Answer 1

f(x) = x² – 4x – 5

a = 1

b = -4

c = -5

$∆ = {b}^{2} - 4.a.c \\ ∆ = ( - 4) {}^{2} - 4.1.( - 5) \\ ∆ = 16 + 20 \\ ∆ = 36 \\ \\ x = \frac{ - b + - \sqrt{∆} }{2.a} \\ \\ x = \frac{ - ( - 4) + - \sqrt{36} }{2.1} \\ \\ x = \frac{4 + - 6}{2} \\ \\ x1 = \frac{4 + 6}{2} = \frac{10}{2} = 5 \\ \\ x2 = \frac{4 - 6}{2} = \frac{ - 2}{2} = - 1$

As raízes ou zeros da função f(x) = x² – 4x – 5 são: -1 e 5.

Espero que tenha ajudado ☺️

Answer 2

Olá!

$f(x)=x^{2} -4x-5~~~~~~~~~~ \to~~~~~~~~~~ a=1~~,~~b=-4~~,~~c=-5\\ \\ \\ \dfrac{-b\pm\sqrt{b^{2}-4\cdot a\cdot c } }{2\cdot a}~~~~\to ~~~~\dfrac{-(-4)\pm\sqrt{(-4)^{2}-4\cdot 1\cdot (-5) } }{2\cdot 1}~~~~\to ~~~~\dfrac{4\pm\sqrt{36} }{2}\\ \\ \\ \\ \dfrac{4\pm6}{2}~~~~ =~~~~\boxed{x'=5~~~e~~~x''=-1}$

Resposta:

raízes:  x' = 5  e  x'' = - 1

:)