Combine like terms.
19/4rs-8/3r+1/4rs+9

The only like terms are 19/4rs and 1/4rs because they have the same variables, so:      [I rearranged, to put the like terms next to each other]

  Since the denominators are already the same, you can combine the fractions

answer:

at time x=0 we have 1000, at time x=1 we have 2000, at time x=2 we have 4000.  

so that's an initial value of 1000 and a ratio of 2,

y = 1000 (2^x)

hope this !