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MaTh = Algebra = help

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Solve this system of linear equaiton by an algebraic method.

So If I had to solve this the elimination method way, how would I do it?

x-2y = 10
3x-y = 0

  • MaTh = Algebra = help -

    x - 2y = 10
    3x - y = 0

    eliminate y by multiplying 3x - y = 0 by -2

    -2(3x - y = 0) = -6x + 2y = 0

    ADD the 2 equations
    x - 2y = 10
    -6x + 2y = 0
    -5x + 0 = 10
    -5x = 10
    x = -2

    substitute x = -2 in x - 2y = 10, to find y

    x - 2y = 10
    -2 - 2y = 10
    -2y = 12
    y = -6

    check x = -2, y = -6
    3x - y = 0
    3(-2) - -6 = 0
    -6 + 6 = 0
    0 = 0

  • MaTh = Algebra = help -

    Oh so You have to multiply it by -2 because the first equation also uses -2 and you have to cancel them out that way right?

    So if its - and + that means you have to add the equations. If its - and - that means you have to subtract and if it's + and + that also means you have to subtract right?

    How did you get -2 as an answer?
    Did you divide 5x by 5 and 10 by five to get 2?

    You lost me right here:
    How did you do this?

    x - 2y = 10
    -2 - 2y = 10
    -2y = 12
    y = -6

    How did you get the second line?
    -2 - 2y = 10?

    And at the end you went 0 = 0
    so they have to equal to zero always?

  • MaTh = Algebra = help -

    How did you get -2 as an answer?
    Did you divide 5x by 5 and 10 by five to get 2? YES

    You lost me right here:
    How did you do this?

    x - 2y = 10
    -2 - 2y = 10
    -2y = 12
    y = -6

    How did you get the second line?
    -2 - 2y = 10?

    to find the value of y, since you know x = -2, you plug x = -2 into either equation and solve for y

    the second line is from plugging -2 in for x in the equation x - 2y = 10

    x = -2
    x - 2y = 10
    -2 - 2y = 10
    -2y = 12
    y = -6

    yes, when you check, both sides will equal 0 if you are correct

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