Question

Determine  as raizes da função f(x)= x2 + 8x +15

Answer 1

Resolve-se basicamente desse jeito, utilizando a fórmula de bhaskara:
x² + 8x + 15
▲= 8² - 4.1.15
▲= 64 - 60
▲= 4

x = - 8 +/- 2 / 2
x1 = -8 -2/ 2 = -10/2 = -5
x2 = -8 +2/2 = -6/2 = -3

Answer 2

Resolvendo por Bháskara.

$x = \dfrac{-b \pm \sqrt{b^2 -4*a*c}}{2*a}$

$a=1, b=8, c=15 \\ \\ \triangle= b^2- 4ac \\ \triangle= (8)^2-4*(1)*(15)\\ \triangle= 64-60 \\ \triangle= 4$

$x = \dfrac{-b \pm \sqrt{\triangle}}{2*a} \\ \\ \\ x = \dfrac{-8 \pm \sqrt{4}}{2*1} \\ \\ \\ x = \dfrac{-8 \pm 2}{2} \\ \\ \\ x' = \dfrac{-8 + 2}{2} \\ \\ \\ x' = \dfrac{-6}{2} \\ \\ \\ x' = -3 \\ \\ \\ x'' = \dfrac{-8 - 2}{2} \\ \\ \\ x'' = \dfrac{-10}{2} \\ \\ \\ x'' = -5$

S = {-3, -5}