Answer:
a = - 1
Step-by-step explanation:
given a quadratic in standard form : y = ax² + bx + c : a ≠ 0
Then the x-coordinate of the vertex is
• = -
The line of symmetry passes through the parabola, hence x-coordinate is 4
y = ax² + 8x - 3 is in standard form
with a = a, b = 8 and c = - 3, hence
- = 4 ( multiply both sides by 2a
- 8 = 8a ( divide both sides by 8 )
a = - 1