A value of a that allows the graph of the given exponential function to contain the point (2, 1/25) include; a = 1/5.
In Mathematics and Geometry, an exponential function can be modeled by using this mathematical equation:

Where:
- a represents the initial value or y-intercept.
- x represents the time or x-variable.
- b represents the rate of change or common ratio.
Since the exponential function must contain the point (2, 1/25), we would substitute each of the coordinates of the point into the function as follows;

By taking the square root of both sides of the exponential function, we have the following:

a = 1/5.