Math Systems

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I cannot solve these last three systems. Could you show me the work for them so i understand how to do them.
1)
x-y=1
2x+y=5
3x-4y=2

2)
5x+8y+6z=14
2x+5y+z=12
-3x+6y-12z=20

3)
x^2+2xy-2y^2=-11
x^2+xy-2y^2=-9

  • Math Systems -

    problem 1
    in the equation x - y = 1, solve for x in terms of y.
    replace x in either of the other two equations and you will be able to solve for x. Now, you can go back to any of the three equations and replace x with the value you found and solve for y.
    Check that your solution for x and y satisfy all three equations.

  • Math Systems - Partial answer -

    1)
    x-y=1
    x = 1 + y

    2x+y=5
    2(1 + y) + y = 5
    2 + 2y + y = 5
    3y = 3
    y = 1

    3x-4y=2
    3x - 4 = 2
    3x = 6
    x = 2

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