1. ## Simplyfying rational expression

I had thought that the common denominator was x-1, but this gives a wrong answer...How do I do the following question correctly?

3/x-1 - 1/x + 2

It looked easy enough..

2. Originally Posted by Charchar
I had thought that the common denominator was x-1, but this gives a wrong answer...How do I do the following question correctly?

3/x-1 - 1/x + 2

It looked easy enough..
Assuming that you meant to write $\displaystyle \frac{3}{x-1}-\frac{1}{x+2}$, I will say that the LCD is $\displaystyle (x-1)(x+2)$

3. Whoops, I should have put 'dividers' or something up to distinguish between terms. I meant:

(3/x-1)-(1/x)+(2)

4. Originally Posted by Charchar
Whoops, I should have put 'dividers' or something up to distinguish between terms. I meant:

(3/x-1)-(1/x)+(2)
Isn't the case that $\displaystyle \frac{1}{2}$ and $\displaystyle \frac{1}{3}$ have different denominators? Analogously, isn't $\displaystyle x-1$ a different number than $\displaystyle x$? So, since they are different, don't we need a common denominator?

What's the first thing that $\displaystyle x$ and $\displaystyle x-1$ will go into? Isn't it $\displaystyle x(x-1)$?

5. Yes, you are right, they are representations of different numbers. Thank you very much, this will prove very valuable on the test!