To find the optimal value of any standard form equation you should first find the axis of symmetry and then substitute it into the equation to find the last value which is the optimal value. The optimal value is the y coordinate of the vertex. Making the optimal value a important thing to find if you would like to solve the parabola.
Here is an example: Find the optimal value of y=12x^2+9x+93 y=12(-3/7)^2+9(-3/7)=93 y=91.31