Answer:
[tex]f( - \frac{b}{2a} )[/tex]
Step-by-step explanation:
When you not given the vertex form, the you are given the standard form:
[tex]f(x) = a {x}^{2} + bx + c[/tex]
The value of k, is the y-value of the vertex of the function.
To find the value of k, you plug in
[tex]x = - \frac{b}{2a} [/tex]
In order works, you evaluate
[tex]f( - \frac{b}{2a} )[/tex]
This will give you the k-value
