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#1 2006-04-04 02:07:24

RauLiTo
Member
Registered: 2006-01-11
Posts: 142

a question in the DETERMINANTS

| X   X²   1 +X³ |
| Y   Y²   1+Y³   | = 0             
| Z   Z ²  1+Z³  |

that was given ...

prove that X Y Z = -1

help please guys i have an exam tomorrow neutral

Last edited by RauLiTo (2006-04-04 02:08:19)


ImPo$$!BLe = NoTH!nG
Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...

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#2 2006-04-04 02:56:56

George,Y
Member
Registered: 2006-03-12
Posts: 1,306

Re: a question in the DETERMINANTS

decompenent the last colume, and reform
| X   X²   1 +X³ |                |1  X   X² |      |1  X   X²|
| Y   Y²   1+Y³   | = -1(- 1)| 1  Y   Y² | +XYZ| 1  Y   Y²| = (1+XYZ)VD 
| Z   Z ²  1+Z³  |                |1  Z   Z ²|         | 1  Z   Z ²|

VD -Vander monde Determinant
if x≠ y≠ z
xyz=-1

Last edited by George,Y (2006-04-04 02:57:31)


X'(y-Xβ)=0

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#3 2006-04-04 04:47:02

RauLiTo
Member
Registered: 2006-01-11
Posts: 142

Re: a question in the DETERMINANTS

thank you very much ... but unfortunately i dind't understand it well ... can someone explain it for me ? !


ImPo$$!BLe = NoTH!nG
Go DowN DeeP iNTo aNyTHinG U WiLL FinD MaTHeMaTiCs ...

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#4 2006-04-04 18:05:07

George,Y
Member
Registered: 2006-03-12
Posts: 1,306

Re: a question in the DETERMINANTS

Reread the determinant properties, and then you will understand
|column1 column2 column3a+column3b|
=|column1 column2 column3a|+|column1 column2 column3b|


X'(y-Xβ)=0

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#5 2006-04-06 12:44:25

George,Y
Member
Registered: 2006-03-12
Posts: 1,306

Re: a question in the DETERMINANTS

Sorry you may not find these properties in your text book
|a  b  c|  |a  b' c|    |a  b+b'  c|
|d  e  f|+|d  e'  f| = |d  e+e'  f|
|g  h  i|   |g  h'  i|     |g  h+h'  i|
see the bottom of this link


other properties used
|

| = k|
|
|
|= - |
| = |
|

Vandermonde Determinant
 
this link

Last edited by George,Y (2006-04-06 12:52:48)


X'(y-Xβ)=0

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