4^x + 4 ^-x = 2 What is the value of X

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4^x + 4 ^-x = 2 What is the value of X [#permalink]

07 Feb 2012, 09:56

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99% (01:30) correct

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based on 7 sessions

4^x + 4^-x = 2 What is the value of x?

a) -1
b) -1/2
c) 0
d) 1/2
e) 1

Thanks

[Reveal] Spoiler: OA

Last edited by Bunuel on 07 Feb 2012, 11:52, edited 1 time in total.

Edited the question

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Re: 4^x + 4 ^-x = 2 What is the value of X [#permalink]

07 Feb 2012, 10:22

nimc2012 wrote:

4^x + 4 ^-x = 2
What is the value of x?

a) -1
b) -1/2
c) 0
d)1/2
e) 1

Thanks

0 (you can try and plug)

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Re: 4^x + 4 ^-x = 2 What is the value of X [#permalink]

07 Feb 2012, 10:50

nimc2012 wrote:

4^x + 4 ^-x = 2. What is the value of x?

a) -1
b) -1/2
c) 0
d)1/2
e) 1

Thanks

Plug-in method should work form most of the people.

Else you can realize that 4^x+\frac{1}{4^{x}}=2 is the sum of a positive number and its reciprocal and it to equal to 2 each must be 1 --> 4^x=1 --> x=0;

Or: let 4^x=a --> a+\frac{1}{a}=2 --> \frac{a^2+1}{a}=2 --> a^2-2a+1=0 --> (a-1)^2=0 --> a=1 --> 4^x=a=1 --> x=0.

Answer: C.
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Re: 4^x + 4 ^-x = 2 What is the value of X [#permalink]

07 Feb 2012, 12:41

thank you so much...it was an easy question!

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Re: 4^x + 4 ^-x = 2 What is the value of X [#permalink]

07 Feb 2012, 14:48

That's easy and thanks for the explanation

Re: 4^x + 4 ^-x = 2 What is the value of X [#permalink] 07 Feb 2012, 14:48

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4^x + 4 ^-x = 2 What is the value of X

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4^x + 4 ^-x = 2 What is the value of X

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