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# What is the solution of 4√x - 4 = 3 * 2√x?

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Senior Manager
Joined: 31 Jul 2017
Posts: 490
Location: Malaysia
GMAT 1: 700 Q50 V33
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WE: Consulting (Energy and Utilities)
What is the solution of 4√x - 4 = 3 * 2√x?  [#permalink]

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Updated on: 09 Sep 2018, 21:12
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00:00

Difficulty:

15% (low)

Question Stats:

76% (00:53) correct 24% (00:40) wrong based on 41 sessions

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What is the solution of 4√x - 4 = 3 * 2√x?

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If my Post helps you in Gaining Knowledge, Help me with KUDOS.. !!

Originally posted by rahul16singh28 on 09 Sep 2018, 21:02.
Last edited by Bunuel on 09 Sep 2018, 21:12, edited 1 time in total.
Renamed the topic and edited the question.
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Joined: 02 Aug 2009
Posts: 7035
Re: What is the solution of 4√x - 4 = 3 * 2√x?  [#permalink]

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10 Sep 2018, 00:18
rahul16singh28 wrote:
What is the solution of 4√x - 4 = 3 * 2√x?

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4√x - 4 = 3 * 2√x
$$4\sqrt{x}-6\sqrt{x}=4.................-2\sqrt{x}=4$$
square both sides..
$$4x=16...............x=4$$

4√x - 4 = 3 * 2√x...........- 4 = 2√x....
Only possible if x is perfect square

D
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Re: What is the solution of 4√x - 4 = 3 * 2√x?  [#permalink]

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10 Sep 2018, 06:28
rahul16singh28 wrote:
What is the solution of 4√x - 4 = 3 * 2√x?

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$$4√x - 4 = 3 * 2√x$$

Or, $$4√x - 4 = 6√x$$

So, $$2√x = - 4$$

Or, $$4x = 16$$ {Squaing both sides}

Or, $$x = 4$$, Answer must be (D)
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What is the solution of 4√x - 4 = 3 * 2√x?  [#permalink]

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11 Sep 2018, 16:49
Abhishek009 wrote:
rahul16singh28 wrote:
What is the solution of 4√x - 4 = 3 * 2√x?

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$$4√x - 4 = 3 * 2√x$$

Or, $$4√x - 4 = 6√x$$

So, $$2√x = - 4$$

Or, $$4x = 16$$ {Squaing both sides}

Or, $$x = 4$$, Answer must be (D)

Hi Abhishek009, thanks for the lucid explanation but I realised on plugging in 4 into the equation. The LHS does not equal the RHS. Why is this

Posted from my mobile device
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Re: What is the solution of 4√x - 4 = 3 * 2√x?  [#permalink]

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11 Sep 2018, 18:27
1
Kem12 wrote:
Abhishek009 wrote:
rahul16singh28 wrote:
What is the solution of 4√x - 4 = 3 * 2√x?

1. 1
2. 2
3. 3
4. 4
5. 5

$$4√x - 4 = 3 * 2√x$$

Or, $$4√x - 4 = 6√x$$

So, $$2√x = - 4$$

Or, $$4x = 16$$ {Squaing both sides}

Or, $$x = 4$$, Answer must be (D)

Hi Abhishek009, thanks for the lucid explanation but I realised on plugging in 4 into the equation. The LHS does not equal the RHS. Why is this

Posted from my mobile device

Hi Kem12,
This question is flawed.

Given, $$4√x - 4 = 3 * 2√x$$

Or, $$4√x - 4 = 6√x$$

So, $$2√x = - 4$$
Divide both sides by -2, we have
$$\sqrt{x}=-2$$

Notice that $$\sqrt{f(x)}$$ can't be negative for all $$x\in \mathbb{R}$$.

Therefore, NO SOLUTION.
_________________

Regards,

PKN

Rise above the storm, you will find the sunshine

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Joined: 02 Sep 2009
Posts: 50619
Re: What is the solution of 4√x - 4 = 3 * 2√x?  [#permalink]

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11 Sep 2018, 20:02
PKN wrote:
Kem12 wrote:
Abhishek009 wrote:
What is the solution of 4√x - 4 = 3 * 2√x?

1. 1
2. 2
3. 3
4. 4
5. 5

$$4√x - 4 = 3 * 2√x$$

Or, $$4√x - 4 = 6√x$$

So, $$2√x = - 4$$

Or, $$4x = 16$$ {Squaing both sides}

Or, $$x = 4$$, Answer must be (D)

Hi Abhishek009, thanks for the lucid explanation but I realised on plugging in 4 into the equation. The LHS does not equal the RHS. Why is this

Posted from my mobile device

Hi Kem12,
This question is flawed.

Given, $$4√x - 4 = 3 * 2√x$$

Or, $$4√x - 4 = 6√x$$

So, $$2√x = - 4$$
Divide both sides by -2, we have
$$\sqrt{x}=-2$$

Notice that $$\sqrt{f(x)}$$ can't be negative for all $$x\in \mathbb{R}$$.

Therefore, NO SOLUTION.

You are right. This is a poor quality question.

Topic is locked.
_________________
Re: What is the solution of 4√x - 4 = 3 * 2√x? &nbs [#permalink] 11 Sep 2018, 20:02
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