# Easy exponential decay

1. Aug 3, 2008

1. The problem statement, all variables and given/known data

In the standard model for exponential decay, y=ab^x , what does a represent and why?

3. The attempt at a solution

I know that a is the value of y when x=0, but I dont understand why this is the case. Any help would be appreciated, thanks.

2. Aug 3, 2008

### Defennder

3. Aug 3, 2008

but i dont understand why though.

4. Aug 3, 2008

### futurebird

What is $$ab^{0}$$ equal to? (As long as $$b \neq 0$$)

5. Aug 3, 2008

is it just a?

6. Aug 3, 2008

### futurebird

Yup. You get that part right?

In this kind of question you want to say what each variable or constant stands for. And then describe how the value of the function changes as x changes.

7. Aug 3, 2008

yeh, what else am I missing?

8. Aug 3, 2008

### futurebird

x stands for time, so when x=0 we know that $$y=a$$ so that's why a is the initial value. As x increases what will happen to $$y=ab^{-x}$$? will it get smaller or larger? why?

9. Aug 3, 2008