Question

11- Qual é a soma das raízes da função f(x) = x2 + 8x – 9? a) – 8 b) 8 c) 1 d) – 9 e) 9

Answer 1

$x^2+8x-9=0\\\\x'=\frac{-8+\sqrt{8^2-4*(-9)}}{2}\\\\x'=\frac{-8+\sqrt{64+36}}{2} \\\\x'=\frac{-8+10}{2}\\\\x'=1$

$x''=\frac{-8-\sqrt{64+36}}{2}\\\\x''=\frac{-18}{2} \\\\x''=-9$

x' = 1

x'' = -9

x' + x'' =

1 -9 = 8

R: Alternativa B.