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# square root X = 25, then x^3 x^ 2 = A. 5^ 12 B. 5^ 20 C.

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Senior Manager
Joined: 02 Dec 2007
Posts: 449
square root X = 25, then x^3 x^ 2 = A. 5^ 12 B. 5^ 20 C. [#permalink]

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19 Sep 2008, 10:38
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square root X = 25, then x^3 – x^ 2 =

A. 5^ 12
B. 5^ 20
C. 6(5^5)
D. 5^4(5^2 + 1)
E. 5^8(5^4 − 1)
Director
Joined: 12 Jul 2008
Posts: 515
Schools: Wharton

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19 Sep 2008, 10:42
1
KUDOS
Nihit wrote:
square root X = 25, then x^3 – x^ 2 =

A. 5^ 12
B. 5^ 20
C. 6(5^5)
D. 5^4(5^2 + 1)
E. 5^8(5^4 − 1)

E

x = 25^2

x^3 – x^ 2 = (25^2)^3 - (25^2)^2
= [(25^2)^2]*(25^2 - 1)
= [((5^2)^2)^2]*[(5^2)^2 - 1]
= [(5^4)^2]*(5^4-1)
= (5^8)*(5^4 - 1)
SVP
Joined: 28 Dec 2005
Posts: 1558

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19 Sep 2008, 14:04
yep, E as well, same method as above
SVP
Joined: 05 Jul 2006
Posts: 1747

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19 Sep 2008, 16:02
Nihit wrote:
square root X = 25, then x^3 – x^ 2 =

A. 5^ 12
B. 5^ 20
C. 6(5^5)
D. 5^4(5^2 + 1)
E. 5^8(5^4 − 1)

x = 5^4 , x^3 – x^ 2 = x^2(x-1) = (5^4)^2 * (5^4 - 1) = 5^8(5^4 - 1) ...E
Re: X   [#permalink] 19 Sep 2008, 16:02
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