Answer:
y = -0.5(x - 4)^2 + 5.
y = -0.5x^2 + 4x - 3.
Step-by-step explanation:
The vertex is at (4, 5). so we have:
f(x) = a(x - 4)^2 + 5
When x = 0 y = -3 so substituting in the above:
- 3 = a(0-4)^2 + 5
-8 = 16a
a = -0.5.
So the vertex form is y = -0.5(x - 4)^2 + 5.
Standard form:
y = -0.5(x^2 - 8x + 16) + 5
y = -0.5x^2 + 4x - 8 + 5
y = -0.5x^2 + 4x - 3.