How do I write this in proper form.

In an assignment of mine we are required to plot a graph and it's table of values, the problem I'm having is the values must not be in decimal form, so for example;

If I have the function below, and I need to find the value for y, if x=-2 how do I find that without it turning it into a decimal. The answer in the practice question says Y=-7/9. I think I understand where the 9 came from, but thats about it (3^{-2} = 1/9)

y = 2(3)^{x }– 1

Anyone care to explain?

Re: How do I write this in proper form.

Quote:

Originally Posted by

**Urpes** In an assignment of mine we are required to plot a graph and it's table of values, the problem I'm having is the values must not be in decimal form, so for example;

If I have the function below, and I need to find the value for y, if x=-2 how do I find that without it turning it into a decimal. The answer in the practice question says Y=-7/9. I think I understand where the 9 came from, but thats about it (3^{-2} = 1/9)

y = 2(3)^{x }– 1

Anyone care to explain?

Ummmmm,... Just put the -2 in?

$\displaystyle y = 2 \cdot 3^{-2} - 1 = \frac{2}{3^2} - 1$

and continue.

-Dan

Re: How do I write this in proper form.

I'm afraid I don't know how to continue any further.

If the next step is

__2__ -1 How do I get -7/9 out of that?

9

Re: How do I write this in proper form.

I hate to say it but if you are taking algebra or preCalculus and can't subtract fraction you have a serious problem! Get "common denominators". You understand that $\displaystyle 1= \frac{9}{9}$, don't you? $\displaystyle \frac{7}{9}- 1= \frac{7}{9}- \frac{9}{9}= \frac{7- 9}{9}= \frac{-2}{9}$.

Re: How do I write this in proper form.