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Wavy Line Method Application - Exercise Question #6

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Wavy Line Method Application - Exercise Question #6  [#permalink]

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26 Aug 2016, 01:47
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Wavy Line Method Application - Exercise Question #6

Find the range of values of x that satisfy the inequality $$\frac{(x-10)^3 (x+7)^5}{(x-5)^5 (x-6)^4} > 0$$

Wavy Line Method Application has been explained in detail in the following post:: http://gmatclub.com/forum/wavy-line-method-application-complex-algebraic-inequalities-224319.html

Detailed solution will be posted soon.
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Wavy Line Method Application - Exercise Question #6  [#permalink]

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26 Aug 2016, 09:05
EgmatQuantExpert wrote:
Wavy Line Method Application - Exercise Question #6

Find the range of values of x that satisfy the inequality $$\frac{(x-10)^3 (x+7)^5}{(x-5)^5 (x-6)^4} > 0$$

Wavy Line Method Application has been explained in detail in the following post:: http://gmatclub.com/forum/wavy-line-method-application-complex-algebraic-inequalities-224319.html

Detailed solution will be posted soon.

Inequality given is $$\frac{(x-10)^3 (x+7)^5}{(x-5)^5 (x-6)^4} > 0$$

We will have the Zero points as -7,5,6 and 10.
Since the power of (x-6)^4 is EVEN, we will not move the curve from 6 to the upside of the line.

So, the range of x will be (-7,5) U (10,infinity)

Please correct me if I am missing anything.
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Re: Wavy Line Method Application - Exercise Question #6  [#permalink]

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18 Nov 2016, 02:26
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2
Solution

Hey Everyone,

Please find below the solution of the given problem.

We see that each factor has a power greater than 1.

We just need to keep in mind that the process is exactly the same: The wavy line passes through the zero point if the power of the corresponding factor is odd. The wavy line bounces back from the zero point if the power of the corresponding factor is even.

(x-6) is the only factor with an even power in the given expression and so the wavy line should bounce back at x = 6.

Plotting the zero points and drawing the wavy line:

Required Range:

-7 < x < 5 or x > 10

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Re: Wavy Line Method Application - Exercise Question #6  [#permalink]

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24 Apr 2018, 05:52
EgmatQuantExpert wrote:
Solution

Hey Everyone,

Please find below the solution of the given problem.

We see that each factor has a power greater than 1.

We just need to keep in mind that the process is exactly the same: The wavy line passes through the zero point if the power of the corresponding factor is odd. The wavy line bounces back from the zero point if the power of the corresponding factor is even.

(x-6) is the only factor with an even power in the given expression and so the wavy line should bounce back at x = 6.

Plotting the zero points and drawing the wavy line:

Required Range:

-7 < x < 5 or x > 10

For x=6 the answer is zero. Sho should the correct answer then be split into:
1) 6 < x < 10
2) 5 < x < 6
3) x < -7
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Wavy Line Method Application - Exercise Question #6  [#permalink]

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24 Apr 2018, 06:29
kritikalal wrote:
EgmatQuantExpert wrote:
Solution

Hey Everyone,

Please find below the solution of the given problem.

We see that each factor has a power greater than 1.

We just need to keep in mind that the process is exactly the same: The wavy line passes through the zero point if the power of the corresponding factor is odd. The wavy line bounces back from the zero point if the power of the corresponding factor is even.

(x-6) is the only factor with an even power in the given expression and so the wavy line should bounce back at x = 6.

Plotting the zero points and drawing the wavy line:

Required Range:

-7 < x < 5 or x > 10

For x=6 the answer is zero. Sho should the correct answer then be split into:
1) 6 < x < 10
2) 5 < x < 6
3) x < -7

We have to find (+) not (-), in this case x = 6 has no meaning for us, since range -7 < x < 5 or x > 10 doesn't include x=6.
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Re: Wavy Line Method Application - Exercise Question #6  [#permalink]

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23 Jul 2018, 02:35
EgmatQuantExpert wrote:
Solution

Hey Everyone,

Please find below the solution of the given problem.

We see that each factor has a power greater than 1.

We just need to keep in mind that the process is exactly the same: The wavy line passes through the zero point if the power of the corresponding factor is odd. The wavy line bounces back from the zero point if the power of the corresponding factor is even.

(x-6) is the only factor with an even power in the given expression and so the wavy line should bounce back at x = 6.

Plotting the zero points and drawing the wavy line:

Required Range:

-7 < x < 5 or x > 10

Hi Payal,

Can you please explain why the exclusion holes are marked at 10 and -7 instead of 5 and 6(following the same strategy as in question 4 and in concepts for wavy line)?

TIA

Thanks,
Sakshi
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Re: Wavy Line Method Application - Exercise Question #6  [#permalink]

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23 Jul 2018, 03:55
1
Hey sakshi.2sep,

We have explained this in detail in our article.
We suggest you go through it once.

Here is the link for the article:
Wavy Line Method Application: http://gmatclub.com/forum/wavy-line-met ... 24319.html

If you still have any doubt, please let us know.
We will be more than happy to resolve your doubt.

Regards,
Ashutosh
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Re: Wavy Line Method Application - Exercise Question #6  [#permalink]

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23 Jul 2018, 04:13
Hi Ashuhtosh,

After going through the article once more, I understand why -7 and 10 are excluded from the solution set but still doubtful if 5 and 6 should also be excluded as they are in the denominator and we should never consider cases where the denominator becomes zero. Please explain why did we not exclude 5 and 6?

Thanks and regards,
Sakshi
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Wavy Line Method Application - Exercise Question #6  [#permalink]

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23 Jul 2018, 04:27
Hey sakshi.2sep,

I have 1 question.

Can we multiply both sides of the inequality by $$(x-5)^10(x-6)^8$$ in the above fraction?
If you do this then inequality will become $${(x-10)^3 (x+7)^5}{(x-5)^5 (x-6)^4} > 0$$

Now, you can solve the inequality.
Hope this helps you.

Regards,
Ashutosh
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Re: Wavy Line Method Application - Exercise Question #6  [#permalink]

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23 Jul 2018, 04:48
Hey Ashutosh,

Thank you. I do get this question in both the forms: denominator and multiplying by square. Just got confused with the holes (exclusions) marked for 2 points(-7,10) of the solution set and NOT marked for other 2 points (5,6) of the solution set in the wavy line representation. However, the answer mentioned as Required Range: -7 < x < 5 or x > 10 has no doubt.

Regards,
Sakshi
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Re: Wavy Line Method Application - Exercise Question #6  [#permalink]

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25 Aug 2018, 07:00
hey EgmatQuantExpert,

You have given great explanation and practice problems.
but I am getting totally confused with starting points of drawing curve.
for above problem, I drew curve starting from top left.
and considered positive parts. where answer is different.

this must be something obvious. but pls help me to get there.
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Re: Wavy Line Method Application - Exercise Question #6  [#permalink]

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25 Aug 2018, 09:57
manasveek wrote:
hey EgmatQuantExpert,

You have given great explanation and practice problems.
but I am getting totally confused with starting points of drawing curve.
for above problem, I drew curve starting from top left.
and considered positive parts. where answer is different.

this must be something obvious. but pls help me to get there.

Hey manasveek,
you need to start drawing the curve from the top right portion.
I am quoting a part of the article that explains the method:

Quote:
How to draw the wavy line?

1. How to start: Once you draw the number line and mark the zero points on the number line, it’s time to draw the wavy line. Start from the top right most portion. Be ready to alternate (or not alternate) the region of the wave based on how many times a point is root to the given expression.

2. How to alternate:
if the power of a term is odd, then the wave simply passes through the corresponding point (root) into the other region (to –ve region if the wave is currently in the positive region and to the +ve region if the wave is currently in the negative region).

I will suggest you go through the whole article: Wavy Line Method Application - Complex Algebraic Inequalities

Also, read our new article about solving inequalities: Solving inequalities- Number Line Method

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Advanced Topics- Permutation and Combination 1 | Permutation and Combination 2 | Permutation and Combination 3 | Probability
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Re: Wavy Line Method Application - Exercise Question #6  [#permalink]

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27 Aug 2018, 22:06
thank you EgmatQuantExpert for such a quick reply.
I tried going through new article and totally understood concept and why is that we start drawing curve from top right.
a very useful article as always by E-gmat.
Thank you very much!

Regards,
Manasvee.
Re: Wavy Line Method Application - Exercise Question #6 &nbs [#permalink] 27 Aug 2018, 22:06
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