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Math Help - help with rearrange equation

  1. #1
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    help with rearrange equation

    just want to ask which is correct way of doing ax + by + x = 0
    example is y = 2x + 8

    y -y = 2x -y + 8 (basically take away y both sides)
    0 = 2x -y + 8

    or

    y - 2x -8 = 2x + 8 - 2x - 8 (instead of taking y away, take 2x + 8 away both sides)
    -2x + y - 8 = 0

    which one is correct?
    thanks for your help in advance.
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  2. #2
    Super Member Quacky's Avatar
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    Re: help with rearrange equation

    Quote Originally Posted by yuenj01 View Post
    just want to ask which is correct way of doing ax + by + x = 0
    example is y = 2x + 8

    y -y = 2x -y + 8 (basically take away y both sides)
    0 = 2x -y + 8

    or

    y - 2x -8 = 2x + 8 - 2x - 8 (instead of taking y away, take 2x + 8 away both sides)
    -2x + y - 8 = 0

    which one is correct?
    thanks for your help in advance.
    The first option was surely far more straightforward? Although either method is correct.
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  3. #3
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    Re: help with rearrange equation

    Quote Originally Posted by Quacky View Post
    The first option was surely far more straightforward? Although either method is correct.
    that is what i was thinking. in da exams, is it acceptable?
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  4. #4
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    Re: help with rearrange equation

    If you multiply either solution by -1 on both sides, you'll find that they're exactly the same.
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  5. #5
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    e^(i*pi)'s Avatar
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    Re: help with rearrange equation

    Quote Originally Posted by yuenj01 View Post
    just want to ask which is correct way of doing ax + by + x = 0
    Do you mean ax+by+c=0?

    Quote Originally Posted by yuenj01 View Post
    example is y = 2x + 8

    y -y = 2x -y + 8 (basically take away y both sides)
    0 = 2x -y + 8

    or

    y - 2x -8 = 2x + 8 - 2x - 8 (instead of taking y away, take 2x + 8 away both sides)
    -2x + y - 8 = 0

    which one is correct?
    thanks for your help in advance.
    Either is correct at Quacky has pointed out. The convention is usually to make the leading term (ax) positive so in this case you would take y from sides but it would be a very petty marker who enforced that
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