# Math Help - Rational expressions

1. ## Rational expressions

I've been looking at the examples in the book and can't find any examples on similar to this problem and I'm trying to figure out how I would go about solving it. Thank You

r- r^2-1/r / 1- r-1/r everything is all divided but I don't know how to write the tags in format.

2. Originally Posted by Rheanna
I've been looking at the examples in the book and can't find any examples on similar to this problem and I'm trying to figure out how I would go about solving it. Thank You

r- r^2-1/r / 1- r-1/r everything is all divided but I don't know how to write the tags in format.
Hi Rheanna,

Parentheses might help. Is this your rational expression?

$\dfrac{r-r^2-\dfrac{1}{r}}{1-r-\dfrac{1}{r}}$

3. Originally Posted by masters
Hi Rheanna,

Parentheses might help. Is this your rational expression?

$\dfrac{r-r^2-\dfrac{1}{r}}{1-r-\dfrac{1}{r}}$
top one is r square 2-1/r
bottom one is r-1/r

it comes out to 1 as the answer but i'm trying to figure out how to come up with that.

4. Originally Posted by masters
Hi Rheanna,

Parentheses might help. Is this your rational expression?

$\dfrac{r-r^2-\dfrac{1}{r}}{1-r-\dfrac{1}{r}}$
Originally Posted by Rheanna
top one is r square 2-1/r
bottom one is r-1/r
You mean like this:

$\dfrac{r-\dfrac{r^2-1}{r}}{1-\dfrac{r-1}{r}}$

5. yes

6. Originally Posted by masters
You mean like this:

$\dfrac{r-\dfrac{r^2-1}{r}}{1-\dfrac{r-1}{r}}$
Alrighty then,

$\dfrac{r-\dfrac{r^2-1}{r}}{1-\dfrac{r-1}{r}}=\dfrac{\dfrac{r^2-(r^2-1)}{r}}{\dfrac{r-(r-1)}{r}}=\dfrac{\dfrac{r^2-r^2+1}{r}}{\dfrac{r-r+1}{r}}=\dfrac{\dfrac{1}{r}}{\dfrac{1}{r}}=1$

7. lol, even staring at the problem i'm still lost.

8. Originally Posted by masters
Alrighty then,

$\dfrac{r-\dfrac{r^2-1}{r}}{1-\dfrac{r-1}{r}}=\dfrac{\dfrac{r^2-(r^2-1)}{r}}{\dfrac{r-(r-1)}{r}}=\dfrac{\dfrac{r^2-r^2+1}{r}}{\dfrac{r-r+1}{r}}=\dfrac{\dfrac{1}{r}}{\dfrac{1}{r}}=1$
Let me do it another way. See if this helps.

Multiply numerator and denominator by r.

$\dfrac{r-\dfrac{r^2-1}{r}}{1-\dfrac{r-1}{r}}$

$\dfrac{r\left(r-\dfrac{r^2-1}{r}\right)}{r\left(1-\dfrac{r-1}{r}\right)}=\dfrac{r^2-r^2+1}{r-r+1}=\frac{1}{1}=1$

9. yeah that r square was confusing me. ugh I know I got 0 on this pre test and Thursday is the test test.