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Math Help - 12 = 11x - 14x

  1. #1
    Junior Member Euclid Alexandria's Avatar
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    Question 12 = 11x - 14x

    Any hints on where I went wrong?

    12 = 11x - 14x
    12 = -3x
    12/-3 = -3x/-3
    -4 = x

    When checking the solution in the original equation, I got the false answer of:

    12 = 11(-4) - 14(-4)
    12 = -44 - 56
    12 = 100
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by Euclid Alexandria
    Any hints on where I went wrong?

    12 = 11x - 14x
    12 = -3x
    12/-3 = -3x/-3
    -4 = x

    When checking the solution in the original equation, I got the false answer of:

    12 = 11(-4) - 14(-4)
    12 = -44 - 56
    12 = 100
    minus times minus is plus.

    so -14(-4)=-(-56)=+56

    RonL
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    Forum Admin topsquark's Avatar
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    Quote Originally Posted by Euclid Alexandria
    Any hints on where I went wrong?

    12 = 11x - 14x
    12 = -3x
    12/-3 = -3x/-3
    -4 = x

    When checking the solution in the original equation, I got the false answer of:

    12 = 11(-4) - 14(-4)
    12 = -44 - 56
    12 = 100
    Also, even though the step that it came from was in error, -44 - 56 = -100.

    -Dan
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  4. #4
    Junior Member Euclid Alexandria's Avatar
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    Unhappy Ok, thanks guys.

    The reason I became confused is, in simplifying equations like

    12 = 11(-4) - 14(-4)

    I thought we were supposed to treat the negative sign in the middle as a subtraction sign. I thought we were to solve the two multiplication problems first, then subtract. I could swear I've seen situations that were similar enough in that vein, to confuse me about this situation. If that's the case, I need to learn to tell the difference.

    Thankfully, at least the variable was correct this time, so I'm improving.
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  5. #5
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by Euclid Alexandria
    The reason I became confused is, in simplifying equations like

    12 = 11(-4) - 14(-4)

    I thought we were supposed to treat the negative sign in the middle as a subtraction sign. I thought we were to solve the two multiplication problems first, then subtract. I could swear I've seen situations that were similar enough in that vein, to confuse me about this situation. If that's the case, I need to learn to tell the difference.

    Thankfully, at least the variable was correct this time, so I'm improving.
    If your teacher will allow it, this might help:
    When I was learning this my teacher always insisted that we write expressions like x-y as x+(-y). That way you never have to worry about whether or not you are adding or subtracting...you are ALWAYS adding.

    Hope it helps!
    -Dan
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  6. #6
    Junior Member Euclid Alexandria's Avatar
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    Thumbs up Thanks for the tip.

    I was doing this for a while, but have been trying to wean myself off of it. I still use it for larger problems, but might continue sticking with it for a while in every case.

    Btw, I finally noticed my error while resolving that equation, so disregard my previous post!
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  7. #7
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by Euclid Alexandria
    I was doing this for a while, but have been trying to wean myself off of it. I still use it for larger problems, but might continue sticking with it for a while in every case.

    Btw, I finally noticed my error while resolving that equation, so disregard my previous post!
    I did that myself for a while. Believe it or not, I've come back to doing it again because the process makes it just SO much easier to find mistakes!

    -Dan
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