Question

Resolva a equação x² – 2x − 8 = 0, sendo U = R.​

Answer 1

$\large \boxed{ \begin{array}{l} x {}^{2} - 2x - 8 = 0 \\ \\ \begin{cases} a = 1 \\ b = - 2 \\ c = - 8 \end{cases} \\ \\ ∆ = b {}^{2} - 4ac \\ ∆ = ( - 2) {}^{2} - 4.1.( - 8) \\ ∆ = 4 + 32 \\∆ = 36 \\ \\ x = \dfrac { - b \pm \sqrt{∆} }{2a} \\ \\ x = \dfrac{ - ( - 2) \pm \sqrt{36} }{2.1} \\ \\ x = \dfrac{2 \pm6}{2} \begin{cases} x_{1} = \dfrac{2 + 6}{2} = \dfrac{8}{2} = 4 \\ \\x_{2} = \dfrac{2 - 6}{2} = \dfrac{ - 4}{2} = - 2 \end{cases} \\ \\ \\S = \{4 \: ; \: - 2 \: \}\end{array}}$

Answer 2

Explicação passo-a-passo:

x²-2x-8=0

a=1

b=-2

c=-8

∆=b²-4ac

∆=(-2)²-4*1*-8

∆=4+32

∆=36

-b±√∆/2a

2±√36/2*1

2±6/2

x¹=2+6/2=8/2=>4

x²=2-6/2=-4/2=>-2