Pre-Calc

Solve the system of equations using either the substitution method or the multiplication/addition method
answer:

3x+2y=14
2x-4y=4

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  1. I would double the first then add that to the 2nd to get
    8x = 32
    x =4
    sub into the first:
    12 + 2y = 14
    2y = 2
    y = 1

    x=4, y =1

    check by subbing those values into both equations, they should work

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    posted by Reiny
  2. thanks so much! do you know how i could check the solution by writing the system as a matrix equation and using the inverse matrix?

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  3. Wow , that would be overkill, but anyway ....

    first of all , it is very difficult to write it in matrix form in this format,
    so you would have the matrix
    3 2
    2-4 multiplied by the column matrix
    x
    y
    =
    14
    4

    I will assume you know how to find the inverse of a 2by2 matrix, and how to multiply matrices
    the inverse of our 2by2 is
    1/4 1/8
    1/8 -3/16

    so
    1/4 1/8
    1/8 -3/16
    multiplied by
    14
    4
    gives us
    4
    1

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    posted by Reiny
  4. ahh thank you and sorry for the overkill

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