The equation of the vertical parabola in vertex form is written as

Where (h, k) are the coordinates of the vertex and p is the focal distance.
The directrix of a parabola is a line which every point of the parabola is equally distant to this line and the focus of the parabola. The vertex is located between the focus and the directrix, therefore, the distance between the y-coordinate of the vertex and the directrix represents the focal distance.

Using this value for p and (3, 1) as the vertex, we have our equation
It is best to make a table for this one
Hour | Cells
0 | 1
1 | 2
2 | 4
3 | 8
4 | 16
5 | 32
6 | 64
7 | 128
After 7 hours, there are 128 cells. To find this, you multiply the starting amount by two each hour.
Answer:
4
Step-by-step explanation: