Question

How do you write the quadratic `F(x)=x^2-4x+9` in vertex form?

Answer 1

Formula for vertex form: `F(x) = a(-b/2a)^2 + f(-b/2a)`

x of vertex: `x = -b/2a = 4/2 = 2`
y of vertex:`y = f(2) = 4 - 8 + 9 = 5`

Vertex form: `F(x) = (x - 2)^2 + 5.`

Check by developing: `F(x) = (x^2 - 4x + 4) + 5 = x^2 - 4x + 9.` OK