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  1. #1
    Out fishing with Annie on his lap, a cigar in one hand and a ginger ale in the other, watching the sunset. Tom Stormcrowe's Avatar
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    Where am I going wrong? Math)

    I can't figure out where I'm going wrong on this.....help please!
    Points A(5,0), B(-1,4) a find slope first
    M AB=(4-0)/(-1-5)=4/-6, so m=-2/3

    y=mx+b
    y=-2/3x+4


    The school server says the correct answer is y=-2/3x+10/3......

    I thought I knew this stuff
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  2. #2
    Senior Member thomson's Avatar
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    b is the y intercept, that is the y point where the line crosses the y axis.
    It is not the difference in y values from two arbitrary points.

  3. #3
    On my TARDIScycle! KingTermite's Avatar
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    b is the y intercept. Once you have the slope, you can plug either point back in and solve for b.

    In the first case:
    0 = -2/3(5) + b
    0 = -10/3 + b
    b=10/3

    Use other point to get same result
    4 = -2/3(-1) + b
    4 - 2/3 = b
    12/3 - 2/3 = b
    10/3 = b

    Either way, you get same y-intercept, so answer is y=-2/3x + 10/3
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  4. #4
    Pokes On Spokes JPradun's Avatar
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    As a visual guide, here is a graph. Above 3, but clearly below 4.

    KingTermite beat me to it regarding the math.
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  5. #5
    Out fishing with Annie on his lap, a cigar in one hand and a ginger ale in the other, watching the sunset. Tom Stormcrowe's Avatar
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    Thanks, I needed a refresher, I guess, as I haven't had to mess with this for a few years.
    . “He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.”- Fredrick Nietzsche

    "We can judge the heart of a man by his treatment of animals." - Immanuel Kant

  6. #6
    Senior Member thomson's Avatar
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    I thought we weren't supposed to give the answer

  7. #7
    riding once again jschen's Avatar
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    Also, check your equation against the original inputs, and you can clearly see that your equation is wrong.
    If you notice this notice then you will notice that this notice is not worth noticing.

  8. #8
    Out fishing with Annie on his lap, a cigar in one hand and a ginger ale in the other, watching the sunset. Tom Stormcrowe's Avatar
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    Yeah, I was just getting stressed out and frustrated. Not a good combination, if you know what I mean. Forest/trees issue. It was all blurring together in frustration.
    . “He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.”- Fredrick Nietzsche

    "We can judge the heart of a man by his treatment of animals." - Immanuel Kant

  9. #9
    riding once again jschen's Avatar
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    No, not a forest/trees issue. Math is not subject to interpretation. One needs to make sure one's fundamental concepts are rock solid and go from there.
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  10. #10
    Administrator CbadRider's Avatar
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    Math! On a Friday night!

    Jeeze ...
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  11. #11
    Senior Member deraltekluge's Avatar
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    How are you with solving systems of simultaneous equations?

    Here's another way of looking at the problem:

    You want to write an equation of the form

    y = mx + b

    You have two sets of values for x and y that will satisfy the equation...plug each set into the equation and get a system of two equations for m and b.

    0 = 5m + b
    4 = -m + b

    Now, solve for m and b.

  12. #12
    Out fishing with Annie on his lap, a cigar in one hand and a ginger ale in the other, watching the sunset. Tom Stormcrowe's Avatar
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    Actually, it was, because I had gotten so frustrated I wasn't thinking straight and couldn't even see a glaring error. I took a break, chilled out and went through the rest of the problems with no issues. I'm extremely right brain dominant, and have always had issues with math.

    Quote Originally Posted by jschen View Post
    No, not a forest/trees issue. Math is not subject to interpretation. One needs to make sure one's fundamental concepts are rock solid and go from there.
    . “He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.”- Fredrick Nietzsche

    "We can judge the heart of a man by his treatment of animals." - Immanuel Kant

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