Exponential and logarithmic functions pls

1) c) y = 500 * 2^x 
In year 1, x = 1 and the population is 500 * 2^1 = 1000
In year 2, this doubles to 500 * 2^2 = 500 * 4 = 2000
ans so on
This model describes the population doubling every year

2) 
A) 3 (1/2)^x and C) (0.25)^x
These numbers reduce as x increases because there is a number with an absolute value less than 1 is being raised to the power of x. They also will never totally reach zero or become negative, but will approach zero as x becomes very large. 

127 millimeters is the answer