Answer:
h(x) = (x +1.5)^2 -20.25
Step-by-step explanation:
We assume you want to rearrange h(x)= x^2 +3x -18.
Recognize the coefficient of x is 3. Add and subtract the square of half that. (3/2)^2 = 9/4 = 2.25
h(x) = (x^2 +3x +2.25) -18 -2.25
Now, write the expression in parentheses as a square, simplify the constant.
h(x) = (x +1.5)^2 -20.25 . . . . . . . . vertex form
You are missing crucial bits of information. If you could reply with the missing information, I will do my best to assist you :)

can be simplified to

, which is an irrational number around 1.732
I hope this helps!