Answer:
y= 7^-t
Step-by-step explanation:
Equation for exponential decay:
An equation represents exponential decay if a term between 0 and 1 is elevated to the independent variable.
In this question:
First option 4 is elevated, so not exponential decay.
Second option:

, thus, the second option represents exponential decay.
28 because 1/4th of 28 is equal to 7
To answer this question, you need to draw out the graph first. By doing so, you will be able to know where the other endpoint is located. (Fig. 1)
Next, count the number from the midpoint to the endpoint to determine the coordinates for the other endpoint. (Fig. 2)
Example: From (2, 5) to (6, 3)
x: 2 to 6 = 4 steps
y: 5 to 3 = 2 steps
From there, you can determine the other endpoint like this.
Example: From (2, 5) to the other endpoint
x: 2 to x1 = 4 steps
y: 5 to y1 = 2 steps
Therefore, x1 = -2 and y1 = 7
Other endpoint: (-2, 7)
Sorry for the messy drawing, it is hard to draw without a pen. Haha... hope this helps :)
Vertex is

and minimum value of f(x) is 12
Hope this helps