How can we prove that \frac{x-1}{x-2} < 1 for x < 0?

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SUMMARY

The discussion focuses on proving that for any x < 0, the inequality \(\frac{x-1}{x-2} < 1\) holds true. Participants analyze the expressions and derive that \(\frac{1}{x-2} < 0\) is a critical component of the proof. The conclusion is reached by manipulating the expression to show that \(\frac{x-1}{x-2} = 1 + \frac{1}{x-2}\) and confirming that \(\frac{1}{x-2}\) is negative, which ensures the entire expression remains less than one.

PREREQUISITES
  • Understanding of rational expressions and inequalities
  • Knowledge of algebraic manipulation techniques
  • Familiarity with limits and behavior of functions as x approaches negative values
  • Basic skills in proving mathematical inequalities
NEXT STEPS
  • Study the properties of rational functions and their asymptotic behavior
  • Learn about algebraic manipulation of inequalities in calculus
  • Explore proofs involving limits and continuity in real analysis
  • Investigate common pitfalls in algebraic proofs and how to avoid them
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Students studying algebra, particularly those tackling inequalities, as well as educators looking for examples of rational function behavior in negative domains.

doubleaxel195
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Homework Statement


I just want to show that given x<0, \frac{x-1}{x-2} &lt;1.


The Attempt at a Solution



I don't know why I am having trouble with this! I feel like this is so easy!

So if x<0, then we know x-1&lt;-1, x-2&lt;-2. So
\frac{-1}{2}&lt;\frac{1}{x-2} and \frac{x-1}{x-2}&lt;\frac{-1}{x-2}.

I can't seem to get a good upper bound on \frac{1}{x-2} that makes the entire thing less than one. Am I doing something illegal? Because now it looks like I should want to get\frac{1}{x-2} &lt;-1 to make it all less than one, but clearly that is not true.
 
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doubleaxel195 said:

Homework Statement


I just want to show that given x<0, \frac{x-1}{x-2} &lt;1.

The Attempt at a Solution



I don't know why I am having trouble with this! I feel like this is so easy!

So if x<0, then we know x-1&lt;-1, x-2&lt;-2. So
\frac{-1}{2}&lt;\frac{1}{x-2} and \frac{x-1}{x-2}&lt;\frac{-1}{x-2}.

I can't seem to get a good upper bound on \frac{1}{x-2} that makes the entire thing less than one. Am I doing something illegal? Because now it looks like I should want to get\frac{1}{x-2} &lt;-1 to make it all less than one, but clearly that is not true.
\displaystyle \frac{x-1}{x-2}=\frac{x-2+1}{x-2}=1+\frac{1}{x-2}

Can you show that 1/(x-2) < 0 ?
 
Yes I can. Thank you so much! Was I doing anything illegal or just picking bad bounds? I can't seem to find a mistake in what I was doing before.
 

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