Given data:
The initial numbers of follower areA=500,000.
The rate at which followers increases is r=19% =0.19.
(a)
The expression for the exponential growth model is,
[tex]F=A(1+r)^t[/tex]Substitute the given values in the above expression.
[tex]\begin{gathered} F=(500,000)(1+0.19)^t \\ =500,000(1.19)^t \end{gathered}[/tex](b)
The value of time is 7 in the year 2019, substitute 7 for t in the above expression.
[tex]\begin{gathered} F=500,000(1.19)^7 \\ =1689,657.7 \\ \approx1690,000 \\ \end{gathered}[/tex]Thus, the expression for the exponential model is f=500,000(1.19)^t, and the followers in the year 2019 is 1690,000.