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Inequalities - General Rule (multiplying two inequalities)

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Manager
Joined: 16 Apr 2010
Posts: 221
Inequalities - General Rule (multiplying two inequalities) [#permalink]

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24 Jul 2010, 01:07
Hi,

Is there any general rule for multiplication or division of two inequalities?

If
a<x<b and c<y<d
then
a+c<x+y<b+d
a-d<x-y<b-c

Now is there any rule to fine xy or x/y?

regards,
Jack
Manager
Joined: 16 Apr 2010
Posts: 221
Re: Inequalities - General Rule (multiplying two inequalities) [#permalink]

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26 Jul 2010, 21:24
Intern
Joined: 03 Mar 2010
Posts: 40
Re: Inequalities - General Rule (multiplying two inequalities) [#permalink]

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28 Jul 2010, 00:58
My proposals is as follows:
1.
0<a<x<b and 0<c<y<d
then ac<xy<bd and a/d<x/y<b/c
2.
a<x<b<0 and c<y<d<0
then ac>xy>bd and a/d>x/y>b/c

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Hardworkingly, you like my post, so kudos me.

Manager
Joined: 16 Apr 2010
Posts: 221
Re: Inequalities - General Rule (multiplying two inequalities) [#permalink]

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03 Aug 2010, 05:47
Help is appreciated :D
Re: Inequalities - General Rule (multiplying two inequalities)   [#permalink] 03 Aug 2010, 05:47
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