Answer:
The number of bacteria  after
 after  days is given by
 days is given by

where  is the initial number of bacteria.
 is the initial number of bacteria.  
Step-by-step explanation:
The number of bacteria  in the sample triples every 10 days, this means after the first 10th day, the number of bacteria is
 in the sample triples every 10 days, this means after the first 10th day, the number of bacteria is 

where  is the initial number of bacteria in the sample.
 is the initial number of bacteria in the sample. 
After the 2nd 10th days, the number of bacteria is 

after the 3rd day, 

and so on.
Thus, the formula we get for the number of bacteria after the <em>n</em>th 10-days is

where  is is the <em>n</em>th 10-days.
 is is the <em>n</em>th 10-days. 
Since,  is 10 days, we have
 is 10 days, we have 

or 

Substituting that into  , we get:
, we get: 
