Quick inequation question (1 Viewer)

[TheFeared]

What do i do for
<a href="http://www.codecogs.com/eqnedit.php?latex=x-\frac{1}{x} > 0" target="_blank"><img src="http://latex.codecogs.com/gif.latex?x-\frac{1}{x} > 0" title="x-\frac{1}{x} > 0" /></a>

Do i times x to the whole inequation and get aa perfect square, graph it and check what parts work?

Thanks

 

[lyounamu]

What do i do for
<IMG title="x-\frac{1}{x} > 0" src="http://latex.codecogs.com/gif.latex?x-\frac{1}{x} > 0">

Do i times x to the whole inequation and get aa perfect square, graph it and check what parts work?

Thanks

x^3 - x > 0
x(x^2-1)>0
x(x+1)(x-1) > 0
solve that

 

[Drongoski]

lyounamu has multiplied both sides of the inequality: x - 1/x > 0 by x² which we know is non-negative. If you multiply by just 'x' instead, say, you cannot be sure since it can be both negative and non-negative - so you can't be sure whether or not you need to reverse the inequality sign '>'.

 

[TheFeared]

Ok, yeah I get it now. It was in my first 3U test, which I basically screwed up.

Yeah, I was thinking it was that, but then I thought, we haven't done this, so i just did the squared. I might actually fail my 3u test :|

 

[4025808]

Ok, yeah I get it now. It was in my first 3U test, which I basically screwed up.

Yeah, I was thinking it was that, but then I thought, we haven't done this, so i just did the squared. I might actually fail my 3u test :|

Well its really easy anyway, so just don't forget