Answer:
standard form: y = x² - 2x - 8
vertex form: y = (x − 1)² - 9
factorized form: y = (x + 2)(x - 4)
Step-by-step explanation:
From inspection of the graph:
- Axis of symmetry: x = 1
- Vertex = (1, -9)
- x-intercepts = (-2, 0) and (4, 0)
- y-intercept = (0, -8)
Standard quadratic form: y = ax² + b x + c
Vertex form of a quadratic equation: y = a(x − h)² + k
If a > 0 then the parabola opens upwards
If a < 0 then the parabola opens downwards
(h, k) is the vertex
c is the y-intercept
Inputting the vertex into the vertex form gives:
y = a(x − 1)² - 9
= a(x² - 2x + 1) - 9
= ax² - 2ax - 8
Using the x-intercepts to create a quadratic equation:
y = a(x + 2)(x - 4)
= a(x² - 2x - 8)
= ax² - 2ax - 8a
Comparing the y-intercepts:
-8 = -8a ⇒ a = 1
Therefore, y = x² - 2x - 8
