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m990540
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i got x>0 or x<-1 too.

But what if we do a cross multiplication then wont we getting 1 > -x => -x<1 => x > -1

so if we compare second line solution with the first line solution how can x>-1 and x<-1 at the same time?Shouldnt we be getting same solution no matter how you do it?

what am i missing?

Bunuel
m990540
Hello,

Other than plugging in numbers, how could you simplify this equation?

1/X > -1

Thanks so much!

\(\frac{1}{x}>-1\) (note you can not cross-multiply and write \(1>-x\) as you don't know the siign of \(x\)) --> \(\frac{1}{x}+1>0\) --> \(\frac{1+x}{x}>0\) --> \(x<-1\) or \(x>0\).

Solving inequalities:
x2-4x-94661.html#p731476
inequalities-trick-91482.html
data-suff-inequalities-109078.html
range-for-variable-x-in-a-given-inequality-109468.html?hilit=extreme#p873535
everything-is-less-than-zero-108884.html?hilit=extreme#p868863

DS questions to practice: search.php?search_id=tag&tag_id=184
PS questions to practice: search.php?search_id=tag&tag_id=189

Hope it helps.
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Spidy001
i got x>0 or x -x => -x x > -1
[/color]
so if we compare second line solution with the first line solution how can x>-1 and x -1

Thanks so much!

\(\frac{1}{x}>-1\) (note you can not cross-multiply and write \(1>-x\) as you don't know the siign of \(x\)) --> \(\frac{1}{x}+1>0\) --> \(\frac{1+x}{x}>0\) --> \(x0\).

Solving inequalities:
x2-4x-94661.html#p731476
inequalities-trick-91482.html
data-suff-inequalities-109078.html
range-for-variable-x-in-a-given-inequality-109468.html?hilit=extreme#p873535
everything-is-less-than-zero-108884.html?hilit=extreme#p868863

DS questions to practice: search.php?search_id=tag&tag_id=184
PS questions to practice: search.php?search_id=tag&tag_id=189

Hope it helps.[/quote][/quote]

You should read the solution you quote carefully: "note you can not cross-multiply and write \(1>-x\) as you don't know the siign of \(x\)".

Never multiply or divide inequality by a variable (or by an expression with variable) unless you are sure of its sign since you do not know whether you must flip the sign of the inequality.



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