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# If n is positive, and r is the remainder when (n-1)(n+1) is

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Manager
Joined: 23 Mar 2006
Posts: 75

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If n is positive, and r is the remainder when (n-1)(n+1) is [#permalink]

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26 Apr 2006, 13:21
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If n is positive, and r is the remainder when (n-1)(n+1) is divided by 24, what is the value of r.

a) n is not divisible by 2
b) n is not divisible by 3

2) Is m+z>0

a) m-3z>0
b) 4z-m>0

Kudos [?]: 1 [0], given: 0

Intern
Joined: 19 Apr 2006
Posts: 28

Kudos [?]: 3 [0], given: 0

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26 Apr 2006, 13:43
hi there

think both problems are best solved with number plug-in

1) c

(n-1)(n+1)=n^2 - 1

to check a) if you plug in 1, 3, 5 you get different r

to check b) if you plug in 1,2,4,5 you get different r

to check c) if you plug in 1, 5, 7, 11 you'll see that r is always 0

2) c as well (but not so sure)

for to check a and b separate the premisses allow to have z and m either with the same sign or with different signs

if you take a and b together the premisses allow you only to use the same sign thus you get an answer for m+z>0

Kudos [?]: 3 [0], given: 0

26 Apr 2006, 13:43
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