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 Post subject: Inequalities - Absolute value
PostPosted: Wed Oct 22, 2008 5:36 am 
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Senior Consultant

Joined: Sun Dec 18, 2005 9:50 am
Posts: 35
Is |a|+ |b|> |a+b| ?

1. a^2 > b^2
2. |a| * b < 0


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 Post subject: Re: Inequalities - Absolute value
PostPosted: Fri Oct 24, 2008 9:59 am 
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Associate

Joined: Mon Oct 20, 2008 2:24 pm
Posts: 1
is it B?


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 Post subject: Re: Inequalities - Absolute value
PostPosted: Tue Oct 28, 2008 5:01 am 
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Senior Consultant

Joined: Sun Dec 18, 2005 9:50 am
Posts: 35
Is |a|+ |b|> |a+b| ?

1. a^2 > b^2
2. |a| * b < 0

1. a^2 > b^2
say a= 4, b= 2, |a|+ |b| = 6, |a+b| = 6, 6>6 -- NO
say a = -4, b = 2, |a|+ |b| = 6, |a+b| = 2, 6>2 -- YES
Inconsistent answers

2.|a| * b < 0 => b<0 as |a|>=0.
so, b is negative and a can be positive or negative.
say a= 4, b= - 2, |a|+ |b| = 6, |a+b| = 2, 6>2 -- YES
say a = -4, b = - 2, |a|+ |b| = 6, |a+b| = 6, 6>6 -- NO
Inconsistent answers

Combine both statements -> a^2 > b^2 and b<0
a can be positive or negative
say a= 4, b= - 2, |a|+ |b| = 6, |a+b| = 2, 6>2 -- YES
say a = -4, b = - 2, |a|+ |b| = 6, |a+b| = 6, 6>6 -- NO

E


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