Answer:
x = - 1
Step-by-step explanation:
Given a parabola in standard form , f(x) = ax² + bx +c ( a ≠ 0 )
Then the axis of symmetry is calculated using
x = - [tex]\frac{b}{2a}[/tex]
f(x) = x² + 2x - 8 ← is in standard form
with a = 1 and b = 2 , then axis of symmetry is
x = - [tex]\frac{2}{2}[/tex] = - 1, that is
x = - 1