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fozzzy
Given \(2^{4x} = 1600\), what is the value of \(\frac{[2^{(x-1)}]^4}{[2^x]^2}\)

A. 2
B. 5/2
C. 5
D. 25/4
E. 24

\(\frac{[2^{(x-1)}]^4}{[2^x]^2}\)

which can be written as

2^{4x - 4 -2x}

2^2x-4

2^2x/16 ---------(a)

\(2^{4x} = 1600\)

2^4x = 40^2

2^{4x*1/2} = 40 ^2*1/2

2^2x = 40

Lets put the value in (a)

40/16 = 5/2

B
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fozzzy
Given \(2^{4x} = 1600\), what is the value of \(\frac{[2^{(x-1)}]^4}{[2^x]^2}\)

A. 2
B. 5/2
C. 5
D. 25/4
E. 24

I need to improve my speed on these questions... Took me 5 minutes because I made careless mistakes and had to re-do the question 3 times.

My reasoning:

We can simply both equations to get the values we need.

\(\frac{[2^{(x-1)}]^4}{[2^x]^2} = \frac{[2^{(4x-4)}]}{[2^x]^2} = \frac{[2^{4x}] +[2^{-4}]}{[2^2x]}\)

From \(2^{4x} = 1600\) we can square both sides by \(\frac{1}{2}\) to get \(2^{2x} = 40\)

Plugging everything back into the question we get

\(\frac{1600}{40*16}\) = \(\frac{5}{2}\)
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2^4x=1600

2^2x=40

2^4x-4 / 2^4

=2^4x-4-2x

=2^2x-4

=2^2x / 2^4

2^2x= 40

2^4 = 16

40/16 = 5/2

B
fozzzy
Given \(2^{4x} = 1600\), what is the value of \(\frac{[2^{(x-1)}]^4}{[2^x]^2}\)

A. 2
B. 5/2
C. 5
D. 25/4
E. 24
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2^4x=1600

2^2x=40

2^4x-4 / 2^4

=2^4x-4-2x

=2^2x-4

=2^2x / 2^4

2^2x= 40

2^4 = 16

40/16 = 5/2

B
fozzzy
Given \(2^{4x} = 1600\), what is the value of \(\frac{[2^{(x-1)}]^4}{[2^x]^2}\)

A. 2
B. 5/2
C. 5
D. 25/4
E. 24
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