+0  
 
0
612
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avatar+1832 

 Nov 28, 2014

Best Answer 

 #8
avatar+129852 
+10

Sorry...I should have been a little more explicit...we have

2 ≥  1/x^2     multiply both sides by x^2

2x^2 ≥ 1       divide both sides by 2

x^2 ≥ 1/2      subtract 1/2 from both sides

x^2 - 1/2 ≥ 0

Does that help ??

 

 Nov 29, 2014
 #1
avatar+33661 
+10

Does this help:

1-1/x^2

Let 1 - 1/x2 = -1 and solve for x to get the limiting values of x at the -1 level

.

 Nov 28, 2014
 #2
avatar+118677 
+10

First be aware that x cannot equal 0

Next muliply everything by x squared

can you do it from there?

 Nov 28, 2014
 #3
avatar+1832 
0

can you do it step by step ? 

 Nov 28, 2014
 #4
avatar+118677 
+5

Hi 315

it's after 3am here and I'm on my phone so my full answer will have to wait till morning.  Sorry  :)

 Nov 28, 2014
 #5
avatar+1832 
0

no problem , thank you 

 Nov 28, 2014
 #6
avatar+129852 
+10

Let's take this in "pieces"

We have

-1 ≤ 1 - 1/x^2  subtract 1 from both sides

-2 ≤ -1/x^2     multiply both sides by -1 and reverse the inequality sign

2 ≥  1/x^2       rearrange

x^2 ≥ 1/2     subtract 1/2 from both sides

x^2 - 1/2 ≥ 0   factor

(x - 1/√2) (x + 1/√2) ≥ 0

And we have two possible intervals that work, here

(-∞, -1/√2] and [1/√2, ∞)

Now, let's look at the other piece

1 - 1/x^2 ≤ 1     subtract 1 from both sides

-1/x^2 ≤ 0         divide by -1 on both sides and reverse the sign

1/x^2 ≥ 0

And the possible intervals here are

(-∞, 0), (0, ∞)

But, we have to take the most "restrictive" intervals that would make the original inequality true

Notice that the interval (-1/√2, 1/√2) makes the original inequality untrue

So, the intervals that "work" are   (-∞, -1/√2] and [1/√2, ∞)

 

 Nov 28, 2014
 #7
avatar+1832 
0

I dont understand this 

 

x^2 ≥ 1/2     subtract 1/2 from both sides

 Nov 29, 2014
 #8
avatar+129852 
+10
Best Answer

Sorry...I should have been a little more explicit...we have

2 ≥  1/x^2     multiply both sides by x^2

2x^2 ≥ 1       divide both sides by 2

x^2 ≥ 1/2      subtract 1/2 from both sides

x^2 - 1/2 ≥ 0

Does that help ??

 

CPhill Nov 29, 2014
 #9
avatar+1832 
0

Thank you CPhill

now its very clear 

 Nov 29, 2014

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