If its 21 inches then rounding to the nearest who should be 21 inches
The vertex form:

The axis of symetry is x = h.

We have

Substitute:

<h3>Answer: x = -3</h3>
I recommend that you download photomath, it is an app that takes a photo of the equation and answers it most of the time.
<span>D. p = fraction H over the quantity 3 times w + a</span>
What’s the question for it?