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avatar+262 

1/X^2-1>=1/X-1

thats what i did:

1/x^2-1 - 1/x-1>=0    *(x+1 )(x-1)

1-1/(x-1)>=0

0/x-1>=0

so now what?how do i need to draw th graph?

 Sep 11, 2015

Best Answer 

 #1
avatar+129849 
+10

Let me show you a way to solve this....    

 

1 / [ x^2 - 1] >= 1/ [x - 1]       and we can write

 

1/[x^2 - 1] - 1/[x - 1]  >= 0     and getting a common denominator, we have

 

-x / [ x^2 - 1] > = 0   

 

Note that this function  does not exist at -1 or 1 because that would make the denominator 0

 

And note that when x = 0, the inequality is true

 

So the solutions  come from one, or more, of these intervals :

 

(-infinity, -1), (-1, 0], [0, 1), (1, infinity)

 

Notice that if x < -1  the inequality is true

 

And if   -1 < x < 0     the inequality is false

 

And if   0 <= x < 1   the inequality is true

 

And if   x > 1, the inequality is false

 

Here's the graph :  https://www.desmos.com/calculator/5qbwbakrao

 

 

cool cool cool

 Sep 11, 2015
 #1
avatar+129849 
+10
Best Answer

Let me show you a way to solve this....    

 

1 / [ x^2 - 1] >= 1/ [x - 1]       and we can write

 

1/[x^2 - 1] - 1/[x - 1]  >= 0     and getting a common denominator, we have

 

-x / [ x^2 - 1] > = 0   

 

Note that this function  does not exist at -1 or 1 because that would make the denominator 0

 

And note that when x = 0, the inequality is true

 

So the solutions  come from one, or more, of these intervals :

 

(-infinity, -1), (-1, 0], [0, 1), (1, infinity)

 

Notice that if x < -1  the inequality is true

 

And if   -1 < x < 0     the inequality is false

 

And if   0 <= x < 1   the inequality is true

 

And if   x > 1, the inequality is false

 

Here's the graph :  https://www.desmos.com/calculator/5qbwbakrao

 

 

cool cool cool

CPhill Sep 11, 2015
 #2
avatar+262 
0

CPhill thank you/I unerstood everuthing thants to you,bu i have another question?is that necessary to add brackets at the denominator ?

 Sep 11, 2015
 #3
avatar+129849 
+5

Yep...we need the brackets because the way you have it written is interpreted as:

 

1/x^2   - 1   >=    1/x - 1           [ the 1's  are separate from the fractions ]

 

Instead of what you intended which is :

 

1/ [x^2 -1 ]   >=  1 /[ x - 1 ]

 

Brackets and parentheses are important......!!!!

 

 

cool cool cool

 Sep 11, 2015

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