Bacteria can be a very fast growing species. One type of bacteria has been known to triple every hour. If the original number of bacteria was 1500, how many bacteria will there be after ‘x’ hours. (You want to demonstrate the number of bacteria from 0 – 48 hours.)

a) Write an equation that models this situation.

i understand how to calculate it and get the answers in one way but I dont know what equation i would use, need an equation that i can graph after

This post was edited by RollOneUp on Nov 20 2022 08:40pm

This reads as a simple exponential function.

Y=ab^x

Where a is your initial value and b is your growth multiplier.

It says your initial value is 1500. a=1500

It says the word triple. This tells you your multiplier is 3. b=3.

x represents time. In this case hours.

y = 1500(3)^x

I can’t upload screenshots here but you can make a table on Desmos and see it’ll always take the previous value and triple it.

Not much to do other than that.

thanks a lot , went up to 6 hours like another question asked and made a graph , just trying to find out now ,

what is the Y - intercept of my graph ? also the shape and rate of increase of graph,

i know it’s exponential growth but can’t remember the name of the shape I know they are looking for something specific xD

The y intercept of any function is f(0).


Plug in 0 for x and evaluate.

In most real cases the y intercept is your initial value. (0,1500).

f(0) = 1500 (3)^0
= 1500 (1)
= 1500
(0,1500)

The shape is either exponential or exponential growth. I can’t imagine a textbook describing any other way.

No idea what you mean by rate of increase. I doubt this is calculus so I don’t think your looking at instantaneous rate of change.

My GUESS is that since b=1 + r this means the rate of increase is 2.

thank you again , life saver