should be simple, where am i going wrong?

• Sep 16th 2008, 07:30 AM
dashreeve
should be simple, where am i going wrong?
[(5)/(x-1) - ((2x)/(x+1))] - 1 is less than 0
when I simplify (get common denom to subtract the 1), i get (-3x^2 + 7x + 6)/(x^2 - 1).
i am assuming i am making an error in the simplification here, but i have checked 3 times. the answers in the back of the book (for zeros) are 1, -1 (from denom, i get this part) and -(2/3) and 3. it's these two i can not get from my numerator. where is my error???
• Sep 16th 2008, 07:49 AM
11rdc11
$\displaystyle \bigg[\frac{5}{x-1}-\frac{2x}{x+1}\bigg] -1 < 0$

$\displaystyle \frac{5x + 5 -2x^2 + 2x -(x^2 -1)}{x^2 -1} < 0$

$\displaystyle \frac{-3x^2 +7x +6}{(x+1)(x-1)} < 0$

Nope that is correct but you have to test and see in what intervals it would be positive and when it would be negative

Look at this post you can use a chart like the one Moo used to see what is going on

http://www.mathhelpforum.com/math-he...76-domain.html
• Sep 16th 2008, 07:51 AM
dashreeve
thanks for the response, thought i was losing my mind. i had checked it 3 times.