Resposta:
alternativa a)
[tex] {x}^{2} - 8x + 7 = 0[/tex]
[tex]a = 1,b = - 8,c = 7[/tex]
[tex]Δ = {b}^{2} - 4ac[/tex]
[tex]Δ = {( - 8)}^{2} - 4.1.7[/tex]
[tex]Δ = 64 - 28[/tex]
[tex]Δ = 36[/tex]
[tex] x = \frac{ - b + - \sqrt{ Δ} }{2a} [/tex]
[tex]x = \frac{ - ( - 8) + - \sqrt{36} }{2.1} [/tex]
[tex] {x}^{'} = \frac{8 + 6}{2} = \frac{14}{2} = {x}^{'} = 7[/tex]
[tex] {x}^{''} = \frac{8 - 6}{2} = \frac{2}{2} = {x}^{''} = 1[/tex]
