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gmatophobia
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I also get 16 as answer and can’t really figure out why it is 9. Can someone pls explain? I’m surely making a mistake with exponential properties, but don’t know which one.

Thanks!

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gmatophobia
­If x is a real number and \(4^{(4^{4})} = 2^{(2^x)}\), what is the value of x ?

A. 7

B. 8

C. 9

D. 16

E. 256

 ­
Attachment:
Screenshot 2024-02-24 152403.png
­­­
­Francesco_8167 Check if this helps

\( ­4^{4} = 4 * 4 * 4 * 4 = 16 * 16 = 256\)

\(4^{(4^{4})} = 4^{256} = (2^2)^{256} = 2^{2*256} = 2^{512}\)­

\(512 = 2^9\)

Hence, the answer is C­
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4^256=2^2^x

=> 2^2.256=2^2^x
=> 2.256=2^x
=>512=2^x

As 1024=2^10, 512=2^9
x=9
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More than anything this is Order of Operations

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

4^256 = 2(2^x)

2^512= 2(2^x)

2^(2^9) = 2(2^x)
2^9=2^x

x=9
gmatophobia
­If x is a real number and \(4^{(4^{4})} = 2^{(2^x)}\), what is the value of x ?

A. 7

B. 8

C. 9

D. 16

E. 256

­
Attachment:
Screenshot 2024-02-24 152403.png
­
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are there more questions of this type to practice?
gmatophobia
­If x is a real number and \(4^{(4^{4})} = 2^{(2^x)}\), what is the value of x ?

A. 7

B. 8

C. 9

D. 16

E. 256

­
Attachment:
Screenshot 2024-02-24 152403.png
­
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gmatophobia
­If x is a real number and \(4^{(4^{4})} = 2^{(2^x)}\), what is the value of x ?

A. 7

B. 8

C. 9

D. 16

E. 256

­
Attachment:
Screenshot 2024-02-24 152403.png
­

Trying to understand why the right answer is right? GMAT Club Tests explanations walk through concepts, shortcuts, and common traps on many questions. See how →

Responding to a pm:

Use the rules of exponents. We know that 4 = 2^2 so we should simplify the LHS.

\(4^{(4^{4})} = (2^2)^{(2^{2*4})} = 2^{(2^{9})}\)
\(2^{(2^x)}\) is the RHS

Hence x = 9
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Hi GMATters,

Here's my video solution to the problem:
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