• May 31st 2008, 07:39 AM
Silver
Find the set of values of x for which

$\frac{x}{x-1} > \frac{2}{3-x}$

thank you :)
• May 31st 2008, 07:57 AM
robocop_911
Quote:

Originally Posted by Silver
Find the set of values of x for which

$\frac{x}{x-1} > \frac{2}{3-x}$

thank you :)

Wh
• May 31st 2008, 08:08 AM
Silver
Quote:

Originally Posted by janvdl
$x(3-x) > 2(x-1)$

$3x-x^2 > 2x-2$

$-x^2 + x + 2 > 0$

$-1(x^2 - x - 2) > 0$

$(x^2 - x - 2) < 0$

$(x - 2)(x + 1) < 0$

$-1 < x < 2$ BUT $x \neq 1$

what about multiplying the both sides by the squared denominators?
Ive answered a similar question like you did and my tutor said it was wrong and told me to use the squared method, which confused the hell outta me.

(by squared denominator i mean this:

$(x-1)^2(3-x)^2 \frac{x}{x-1}>\frac{2}{3-x} (3-x)^2(x-1)^2$)
• May 31st 2008, 08:14 AM
Krizalid
Quote:

Originally Posted by janvdl

$x(3-x) > 2(x-1)$

This has to be wrong. You can't multiply by $x-1$ or $3-x$ since we don't previously know what their signs are.

We first gonna have to make some algebra:

\begin{aligned}
\frac{x}{x-1}&>\frac{2}{3-x} \\
\frac{x}{x-1}+\frac{2}{x-3}&>0 \\
\frac{x^{2}-3x+2x-2}{(x-1)(x-3)}&>0 \\
\frac{(x+1)(x-2)}{(x-1)(x-3)}&>0.
\end{aligned}