Given that there were 30 bacteria present originally.
a=30
Also given that the number doubles every one hour.
After one hour the count =2×30=60
Since the count doubles every hour it forms a G.P. with r=2
a,ar,ar2........
The count at the end of 2nd hour=ar^2=30×2^2=120
The count at the end of 4th hour=ar^4=30×2^4=480
The count at the end of 8th hour=ar^8n=30×2^8=7680
etc.
The count at the end of n^th hour=ar^n=30×2^n
Also, the equation y=30*(2)^8/1 give the same result y= 7680