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555-605 (Medium)|   Algebra|      
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sanjoo
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What is the value of x? Updated on: 15 Feb 2014, 02:52
Originally posted by sanjoo on 14 Feb 2014, 09:27.
Last edited by Bunuel on 15 Feb 2014, 02:52, edited 2 times in total.
Edited the question.
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

35% (medium)

Question Stats:

67% (01:19) correct 33% (01:22) wrong based on 152 sessions

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What is the value of x?

(1) 4x^2 - 4x + 1 = 0
(2) 4x^2 - 1 = 0
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A
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What is the value of x? 14 Feb 2014, 11:08
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Quote:
What is the value of X?

1) 4x^2-4x-1=0
2)4x^2-1=0
Show more

There is a mistake in your question :)

I think it should be
1) 4x^2-4x+1=0

shouldn't it ?

With the new version the answer is indeed A otherwise there is no answer :?
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sanjoo
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What is the value of x? 14 Feb 2014, 12:11
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GMarc
Quote:
What is the value of X?

1) 4x^2-4x-1=0
2)4x^2-1=0

There is a mistake in your question :)

I think it should be
1) 4x^2-4x+1=0

shouldn't it ?

With the new version the answer is indeed A otherwise there is no answer :?
Show more


yes .. its + sign.

Edited !
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What is the value of x? 15 Feb 2014, 02:52
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What is the value of x?

(1) 4x^2 - 4x + 1 = 0 --> recognize the square of the difference: \(4x^2 - 4x + 1 = (2x-1)^2=0\) --> \(2x-1=0\) --> \(x=\frac{1}{2}\). Sufficient.

(2) 4x^2 - 1 = 0 --> \(x^2=\frac{1}{4}\) --> \(x=\frac{1}{2}\) or \(x=-\frac{1}{2}\). Two different answers. Not sufficient.

Answer: A.
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What is the value of x? 14 Aug 2014, 06:36
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What is the value of X?

1. 4.x^2-4.x+1=0
a=4, b=-4, and c=1. Use the quadratic formula: (-b +/- (Sqrt(b^2-4.a.c))/2a). Put the values and the discriminant, i.e. sqrt(b^2-4ac) becomes zero. This mean there is only 1 root which we don't have to calculate. SUFFICIENT

2. 4x^2-1=0
4x^2=1
x^2=(1/4)
x=sqrt(1/4)
x=1/2 OR -1/2 INSUFFICIENT

Therefore answer is A.
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