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angela210793

  • 2 years ago

Matrix

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  1. angela210793
    • 2 years ago
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    I thought to multiply the first row with 1/3...|dw:1329578934017:dw|

  2. nenadmatematika
    • 2 years ago
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    that would be a good idea angela :D

  3. angela210793
    • 2 years ago
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    i can make the first element in the second row 0 but i can't go further :(

  4. bahrom7893
    • 2 years ago
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    what's r? reduced row echelon?

  5. angela210793
    • 2 years ago
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    idk wht u call it...i'm asking for the range

  6. nenadmatematika
    • 2 years ago
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    why? multiply the first row with -4 and add to the third row to get 0 under

  7. amistre64
    • 2 years ago
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    colA is the range of a matrix A right?

  8. amistre64
    • 2 years ago
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    row reduce to determine your pivot points; and all columns with a pivot point define colA

  9. angela210793
    • 2 years ago
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    I'm sorry i don't get it..wht is colA???

  10. amistre64
    • 2 years ago
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    as far as I can tell, thats the american version of range of a matrix

  11. nenadmatematika
    • 2 years ago
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    |dw:1329579146175:dw|

  12. amistre64
    • 2 years ago
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    can you type in the rows? a b c d e f g h like that cause its hard to read .... well, nenands is a bit clearer

  13. nenadmatematika
    • 2 years ago
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    |dw:1329579294854:dw|

  14. amistre64
    • 2 years ago
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    your matrix I believe will simplify to 3 linearly independant column vectors; or less. that will tell us the range or span

  15. angela210793
    • 2 years ago
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    :O:O:O:O How nenad?????? in the example my teacher has solved she has had the elements of the diagonal =1 :O

  16. angela210793
    • 2 years ago
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    has made***

  17. amistre64
    • 2 years ago
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    turning it into row reduced is extra work becasue the pivots dont change

  18. nenadmatematika
    • 2 years ago
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    no Angela I'm sure this is the solution...it's quite easy...do you know the procedure to get the rank of the matrix?

  19. angela210793
    • 2 years ago
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    i know the theory but i don't know how to use tht in practice -_-

  20. angela210793
    • 2 years ago
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    how did u know u should have changed R1with R3???

  21. nenadmatematika
    • 2 years ago
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    well this is how you start...first you take a look at the first element of the matrix (first row and the first column)....if it's different from zero then you call it ''the pivot''. OK? Now you make zeros under that first pivot using muliplication with some number and adding to the row below....that's how you make the zeros under the first pivot. Then you look for another pivot...you follow the main diagonal and if it's different from zero then it's a second pivot and you make zeros under that number...you continue with this procedure until you're finished....the final rank is the number of elements on the main diagonal different from zero, so the number of pivots...in this case I have three pivots so the rank is 3

  22. angela210793
    • 2 years ago
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    Hmmmm.....ok thanks guys :):)

  23. nenadmatematika
    • 2 years ago
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    >> rank([3 6 9 3;2 -5 3 0;4 -10 10 4]) ans = 3

  24. nenadmatematika
    • 2 years ago
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    Matlab says it's 3 also so your teacher is tripping :D

  25. angela210793
    • 2 years ago
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    I'm really hopeless...:(:( thank you very much :) both of u :)

  26. nenadmatematika
    • 2 years ago
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    angela don't go...I can show you some examples so you can learn the procedure? I can give you some matrix and we'll work on it together OK?

  27. angela210793
    • 2 years ago
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    yes yes yes :)

  28. nenadmatematika
    • 2 years ago
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    ok here is one for begining:|dw:1329580248289:dw|

  29. nenadmatematika
    • 2 years ago
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    now tell me what is the first element of this matrix and is it different from zero?

  30. angela210793
    • 2 years ago
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    since the first element f the matrix is 1 then the first element of R2 must be 0???

  31. angela210793
    • 2 years ago
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    is the rank 1?? O.o

  32. angela210793
    • 2 years ago
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    range***

  33. nenadmatematika
    • 2 years ago
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    OK it's 1...so that is the first pivot...now do some operations to make 0 under that 1....the easiest way is to multiply the first row with -3 and to the second row...draw that so I can see OK?

  34. nenadmatematika
    • 2 years ago
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    add*

  35. angela210793
    • 2 years ago
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    |dw:1329580611324:dw|

  36. nenadmatematika
    • 2 years ago
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    that's great...now since you made zero under that 1, the next step is to look for the next pivot(element different from zero) on the main diagonal....it's number -2....so you have to make zeros under that pivot...but since there are no more elements under that -2 the transformations are done and now you can read the rank of the matrix....the rank is the number of row where at least one element is different from zero, or you can count the number of pivots(elements on the main diagonal different from zero)...so what is the rank?

  37. RagingSquirrel
    • 2 years ago
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    *Clicks on question thinking it's about the matrix* DANGIT

  38. nenadmatematika
    • 2 years ago
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    number of rows*

  39. angela210793
    • 2 years ago
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    so the range is 2???

  40. nenadmatematika
    • 2 years ago
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    correct Angela!!! :D just to be clear here in Serbia we call it rang, but I read this material from the American matematicians and I'm sure they use the term ''rank''

  41. angela210793
    • 2 years ago
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    haha :) can we work on some more examples pleaseeeee

  42. nenadmatematika
    • 2 years ago
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    of course....check this one:|dw:1329580900431:dw|

  43. angela210793
    • 2 years ago
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    |dw:1329581058847:dw|

  44. nenadmatematika
    • 2 years ago
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    yes :D

  45. angela210793
    • 2 years ago
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    |dw:1329581078055:dw|

  46. nenadmatematika
    • 2 years ago
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    no...we must make a deal here....it's very important the way you make zeros...you can't do it anyway you want...first you make the zeros under that 1. So multiply the first row with -2 and add to the second row....in the third row you already have zero so you don't touch that third row OK.? draw again...:D

  47. angela210793
    • 2 years ago
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    no way :(:(|dw:1329581327917:dw|

  48. nenadmatematika
    • 2 years ago
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    great it's correct now what is the next pivot you see?

  49. angela210793
    • 2 years ago
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    10????

  50. nenadmatematika
    • 2 years ago
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    that's my girl....now make zeros under that pivot....

  51. angela210793
    • 2 years ago
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    xD just a thought...how abt R1-2R3???

  52. angela210793
    • 2 years ago
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    tht won't work will it???

  53. nenadmatematika
    • 2 years ago
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    you don't touch the first row anymore...you made zeros under the first pivot, so you now operate with the second row....for example multiply the second pivot with -1/5 and add to the third row...

  54. nenadmatematika
    • 2 years ago
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    |dw:1329581919090:dw|

  55. angela210793
    • 2 years ago
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    |dw:1329582143630:dw|

  56. nenadmatematika
    • 2 years ago
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    what is the third pivot now?

  57. angela210793
    • 2 years ago
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    5??? but there's no 0 under it O.o

  58. nenadmatematika
    • 2 years ago
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    that's right....that means no more transformations with the matrix so what is the rank?

  59. angela210793
    • 2 years ago
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    3??

  60. nenadmatematika
    • 2 years ago
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    yes

  61. angela210793
    • 2 years ago
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    ur a genius xD :) Can i borrow ur brain???????

  62. nenadmatematika
    • 2 years ago
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    wait we must do one more :D

  63. angela210793
    • 2 years ago
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    sure :)))

  64. nenadmatematika
    • 2 years ago
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    |dw:1329582383881:dw|

  65. nenadmatematika
    • 2 years ago
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    haha :D

  66. angela210793
    • 2 years ago
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    how abt R1-2R3???

  67. nenadmatematika
    • 2 years ago
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    no problem :D OK Angela what is the first number you see?

  68. angela210793
    • 2 years ago
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    |dw:1329582684252:dw|

  69. angela210793
    • 2 years ago
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    OMG wait.... will i be the stupid girl who didn't get a single thing? :O:O:O

  70. nenadmatematika
    • 2 years ago
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    OK I hope we both agree that is unconvenient to perform ''zero making'' under that 13...so one of the possibilities is to exchange the first and the third column because the third column is filled with ''beautiful numbers '' for addition, multiplication etc do it

  71. angela210793
    • 2 years ago
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    i was just going to ask if we could change C3 with C1 :)

  72. angela210793
    • 2 years ago
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    |dw:1329582859078:dw|

  73. nenadmatematika
    • 2 years ago
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    now you work and I watch....:D

  74. angela210793
    • 2 years ago
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    |dw:1329582907187:dw|

  75. nenadmatematika
    • 2 years ago
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    |dw:1329582876260:dw|

  76. angela210793
    • 2 years ago
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    |dw:1329583007088:dw|

  77. angela210793
    • 2 years ago
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    ahhhhaaaa...i just wanted ur confirmation ;) :P

  78. angela210793
    • 2 years ago
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    |dw:1329583049393:dw|

  79. nenadmatematika
    • 2 years ago
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    |dw:1329583024634:dw|

  80. angela210793
    • 2 years ago
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    |dw:1329583163929:dw|

  81. nenadmatematika
    • 2 years ago
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    |dw:1329583152017:dw|