Question 1007696
How to find this yourself:


Two ways.


One way, use formula for general solution of quadratic equation to find the zeros, identify the value exactly in the middle of the zeros, plug this value into the function, and evaluate the value.  That is the maximum value for your function.


Another way, is use Competing the Square to convert your function from general form, to standard form, and you can read the coordinates for the maximum (which is the vertex) directly from the standard form.


Choosing the first way described, you should need no help.  Choosing the standard form / complete the square way, do you need help?


ANSWER:
Vertex is {{{system(x=13/6, highlight(y=61/12))}}}.