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March 30, 2017

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2x + y = -5
3x +5y = 3

How come I have to multiply by 5 to make the y variables cancel, like what does that mean? I don't get how ur supposed to multiply like where and how? Im really stuck right now, please help:(

  • Necessary Math HELp - ,

    2x + y = -5
    3x +5y = 3

    to solve 2 equations simultaneously (at the same time), by elimination, the object is to get rid of one variable.

    adding a negative to a positive equals zero, for example, 5y + -5y = 0.

    So, to get rid of y in the above 1st equation, since the first equation has just "y" and the second equation has "5y", you multiply the first equation by -5 to get "-5y" so that the -5y added to 5y = 0,

    Multiply the whole equation by -5

    -5 (2x + y = -5) = -10x - 5y = 25

    Now add the two equations together
    -10x - 5y = 25
    3x + 5y = 3
    -7x + 0 = 28
    -7x = 28
    x = -4

    substitute x = -4 in either equation and solve for your y value

    do you understand this?

  • Necessary Math HELp - ,

    Wow helper:D
    Thanks a lot buddy, I really appreciate all the time you put to help me with my question. Yeah thanks to your explanation I get it, thanks a lot:)

    So here's how I substitute right?

    2x+y = -5
    2(-4)+y = -5
    -8 +y = -5
    Then I add 8 to both sides and get:
    y = -3

    Therefore the solution would be:
    (-4,3)

  • Necessary Math HELp - ,

    correct, the answer is (-4, 3)

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