The answer would be 7.07 if you are using the whole pi
Using the quadratic equation instead of calculus, you can find the x coordinate of the vertex as it will be the midpoint of the two x coordinates of the zeros...
x=(-3±√-27)/2
x=-1.5±√-6.75
That the second term is imaginary does not matter because we will add or subtract this value from -1.5, thus the midpoint of the zeros, the x coordinate of the vertex is -1.5. And to find the value of y for the vertex we just find the value of y when x=-1.5
y(-1.5)=6.75
Since y>0, the vertex is above the x-axis.
As I understood your typing <span>3 1/4 means

So,
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Is it what you are looking for?
Answer:
4 or 
Step-by-step explanation:
I used M a t h w a y. it's really helpful. Good luck.