Answer
$$1200(0.6)^t$$
Work Step by Step
Note that $\frac{720}{1200} = \frac{432}{720} = \frac{259.20}{432} = \frac{155.52}{259.2} = 0.6$
So, each next number is 0.6 times the previous number.
$$y(t+1) = 0.6y(t)$$
We are given that it is an exponential function so $$y(t)=Cb^t$$
By this, we get,$Cb^{t+1}= 0.6Cb^t$
Or $$b=0.6$$
Putting t = 0 gives, $y(0) = Cb^0 =1200$
Or $$C = 1200$$
Therefore, $$\boxed{y=1200(0.6)^t}$$
