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# What is the value of x?

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Math Expert
Joined: 02 Sep 2009
Posts: 58427
What is the value of x?  [#permalink]

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16 Jul 2017, 23:10
00:00

Difficulty:

85% (hard)

Question Stats:

41% (02:35) correct 59% (01:59) wrong based on 85 sessions

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What is the value of x?

(1) $$4^x − 20*2^x + 64 = 0$$

(2) $$4^x = x^4$$

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Math Expert
Joined: 02 Aug 2009
Posts: 8006
Re: What is the value of x?  [#permalink]

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17 Jul 2017, 01:11
Bunuel wrote:
What is the value of x?

(1) $$4^x − 20*2^x + 64 = 0$$

(2) $$4^x = x^4$$

Hi...

Lets see the statements..
(1) $$4^x − 20*2^x + 64 = 0$$
To solve this let's take $$2^x=a$$..
So $$a^2-20a+64=0........(a-16)(a-4)=0$$..
So a=16 or a=4..
Or $$2^x=16...X=4.......2^x=4..X=2$$
Two values, 2 and 4 possible
Insufficient

(2) $$4^x = x^4$$
Clearly x cantake value of 2 or 4..
Insuff

Combined
X as 2 or 4 still exists
Insufficient

E
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Re: What is the value of x?  [#permalink]

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28 Jan 2019, 23:01
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Re: What is the value of x?   [#permalink] 28 Jan 2019, 23:01
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