What would the equation be

What would the graphing equation be for the following?

A population starting at 2200 decreases at a rate of 10% each year.

P = 2200 x (0.90)^t

2200 is the starting, 0.90 because it'll be left with 90% of what it had before.

So 2200 x (0.90)^1 for example, will give 1980. Then 2200 x (0.90)^2 should give 1782.

So on and so forth.

the function is
p(x) = 0.9^x
x in years
http://imageshack.us/a/img33/250/spaziod…