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m23chris

  • 3 years ago

solve using row reduction: 4x+9y=1 3x+7y=1

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  1. .Sam.
    • 3 years ago
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    row reduction=elimination?

  2. m23chris
    • 3 years ago
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    im not exactly sure what you mean

  3. m23chris
    • 3 years ago
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    im trying to find x and y

  4. .Sam.
    • 3 years ago
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    http://en.wikibooks.org/wiki/Linear_Algebra/Row_Reduction_and_Echelon_Forms

  5. shivam_bhalla
    • 3 years ago
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    @.Sam. ,you are right

  6. .Sam.
    • 3 years ago
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    First make x the same 4x+9y=1 times 3 3x+7y=1 times 4 ------------------------------------- 12x+27y=3 12x+28y=4 ======== -y=-1 y=1 4x+9y=1 4x+9(1)=1 4x+9=1 Solve for x

  7. m23chris
    • 3 years ago
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    x=1 y=-1?

  8. jim_thompson5910
    • 3 years ago
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    well row reduction deals with matrices and elimination deals with systems of equations, so they're slightly different, but they get you the same answer.

  9. m23chris
    • 3 years ago
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    i need to solve it using the matrix

  10. shivam_bhalla
    • 3 years ago
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    see here @m23chris : http://www.math.hmc.edu/calculus/tutorials/linearsystems/

  11. m23chris
    • 3 years ago
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    we never really did it like this its hard to understand

  12. jim_thompson5910
    • 3 years ago
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    4x+9y=1 3x+7y=1 4 9 1 3 7 1 1 9/4 1/4 (1/4)*R1 3 7 1 1 9/4 1/4 0 1/4 1/4 R2 - 3*R1 ---> R2 1 9/4 1/4 0 1 1 4*R2 1 0 -2 R1 - (9/4)*R2 ---> R1 0 1 1 So the solutions are x = -2 and y = 1

  13. m23chris
    • 3 years ago
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    so youre dividing by 4 in the first row

  14. jim_thompson5910
    • 3 years ago
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    yes in the third step

  15. m23chris
    • 3 years ago
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    ok i get it now but i have 2 more questions involving 3 rows using the matrix can you help me?

  16. jim_thompson5910
    • 3 years ago
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    sure, just make a new question and let me know about it

  17. m23chris
    • 3 years ago
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    ok

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