Question

f(x)=x²+8x+15
o zero da função ?

Answer 1

delta = 64 - 60
delta = 4
x = -8 +- raiz de 4 / 2
x = -8 +- 2/2
x´= -6 / 2 = -3
x´´ = -10/2 = -5         ok

Answer 2

$delta= b^2-4*ac \\ delta=8^2-4*1*15 \\ delta=64-60 \\ delta=4 \\ \\ -b+- \frac{\sqrt{delta} }{2*a} \\ x= \frac{-8+-2}{2} \\ x1= \frac{-8+4}{2} \\ x2= \frac{-8-4}{2} =-5$