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# Algebra....aproach?

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Joined: 09 Jun 2009
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Algebra....aproach? [#permalink]  08 Nov 2009, 13:53
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0% (00:00) correct 100% (01:58) wrong based on 0 sessions
a,b,c and d are four +ve real nubers such that abcd=1, what is the minimum value of
(1+a)(1+b)(1+c)(1+d)?

a) 4
b) 1
c) 16
d) 18

what is the best way to solve such question where in we need to calculate the min or max values?
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Joined: 02 Sep 2009
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Re: Algebra....aproach? [#permalink]  08 Nov 2009, 15:28
papillon86 wrote:
a,b,c and d are four +ve real nubers such that abcd=1, what is the minimum value of
(1+a)(1+b)(1+c)(1+d)?

a) 4
b) 1
c) 16
d) 18

what is the best way to solve such question where in we need to calculate the min or max values?

Think there is no catch in this question. As the numbers are positive and their product is 1: either 2,3, or all 4 numbers are reciprocals and rest is 1 OR all numbers are equal to 1.

Minimum value will be when a=b=c=d=1, hence (1+a)(1+b)(1+c)(1+d)=16. (You can try reciprocals to see that the product will be greater)

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Re: Algebra....aproach?   [#permalink] 08 Nov 2009, 15:28
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