Complete the square of ax^2+bx+c where b=0

I'm sure the method is just slipping my mind, and I've done this before, but only once since I cannot find an example in my book.

The question is stated like this.

The path of a basketball shot can be modelled by the equation h=-0.125d^2+2.5, where h is the height of the basketball, in meters, and d is the horizontal distance of the ball from the person, in meters.

a) Find the maximum height reached by the ball.

b)What is the horizontal distance of the ball from the player when it reaches its maximum height?

We have been doing completing the square to get equations of standard form (y=ax^2+bx+c) to vertex form (y=a(x-h)+k) in order to solve these questions. But with bx=0 , what do I do here? Can someone provide the steps?

Thanks in advance!