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Math Help - slope-intercept to standard form

  1. #1
    Newbie dizzycarly's Avatar
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    slope-intercept to standard form

    I am a little confused with this one and I have a test tomorrow

    Why does y = -3x -3 (slope-intercept form) become 3x + y + 3 = 0 in standard form instead of -3x-y-3 = 0?

    and - 3 = y-(-10)/x-1 should be - 3x-y-7 = 0 so why is it 3x+y+7 = 0?

    Mind explaining? Thanks so much!
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  2. #2
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    They've just multiplied everything by -1 to make it a bit cleaner.
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  3. #3
    Newbie dizzycarly's Avatar
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    do you always have to time it by (-1)?
    Why does is my asnwer always the opposite charge.
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  4. #4
    No one in Particular VonNemo19's Avatar
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    Quote Originally Posted by dizzycarly View Post
    I am a little confused with this one and I have a test tomorrow

    Why does y = -3x -3 (slope-intercept form) become 3x + y + 3 = 0 in standard form instead of -3x-y-3 = 0?

    and - 3 = y-(-10)/x-1 should be - 3x-y-7 = 0 so why is it 3x+y+7 = 0?

    Mind explaining? Thanks so much!
    y=-3x-3
    Subtracting y from both sides
    y-y=-3x-y-3
    0=-3x-y-3
    -3x-y-3=0

    It is good to note here that if we would have added (3x+3) to both sides, the problem would have been more aesthetically pleasing while maintaining equivalency:

    y=-3x-3
    y+(3x+3)=-3x-3+(3x+3)
    y+3x+3=0

    This form is not only equivalent to the other, but more conventional, and therefore what your teacher is going to be looking for first. Both answers are correct.

    By the way, I like your avatar.
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  5. #5
    Master Of Puppets
    pickslides's Avatar
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    Quote Originally Posted by dizzycarly View Post
    do you always have to time it by (-1)?
    Why does is my asnwer always the opposite charge.
    Nope, this is only done to make things look less complex. Multiply through by -1 if there is an abundance of negative terms.
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