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exponents prob 3.....

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Re: exponents prob 3.....

by sureshbala » Mon Feb 09, 2009 2:50 pm
willbeatthegmat wrote:If 4^4x= 1600, what is the value of (4^x-1)^2?

40
20
10
5/2
5/4

[spoiler]OA 5/2[/spoiler]
Given 4^4x = 1600. We need to find [4^(x-1)]^2 i.e 4^(2x-2) [since (a^m)^n = a^(mn)]

Since 4^4x = 1600
(4^4x)^1/2 = 40
i.e 4^2x = 40 (4^2x is nothing but the sqrt of 4^4x)

Now 4^(2x-2) = 4^2x/4^2 = 4^2x/16 = 40/16 = 5/2
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