the form of a parabola has the form

when t=0

usinc the graphic when t = 0 the value on the y axis is 45

now using the formula for the vertex:

since h=0

the only possible way for this to be 0 is if the numerator is equal to 0, reason why b is 0
now using the point given, we find a

re write the equation

there is not h, inside the parentheses beacuse h=0
Does the equation makes sense?
Yes, because the number accompanying the x^2 the parabola is upside-down, also the vertex its on (0,45) menaing the parabola moved 45 units up.
Also since the hammer is dropping the y should become less ultil it gets to the floor.