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Math Help - Slope-Intercept form shortcut?

  1. #1
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    Slope-Intercept form shortcut?

    In class today, my teacher was going over a shortcut you can take in slope-intercept form working. Unfortuneately, i was half-dozing throughout the class, because i spent so much time yesterday working on social studies and language projects, and i had 2 hours of volunteer working, that i only got about 4 hours of sleep. Due to this, I have no clue how to do the shortcut. does anyone know of this shortcut, and how to work it?
    here's a couple problems from each category we're supposed to do...
    "Write the equation in slope-intercept form." (Note, we do not have to graph them.)
    4x+5y=15

    4x-y-3=0

    x-y=0

    "Decide whether the graphs of the two equations are parallel lines. Explain your answer."
    y=-3x+2; y+3x=-4

    2x-12=y; y=10+2x

    y+6x-8=0; 2y=12x-4

    thanks in advance. and dont worry, no more projects for a while, so i should be able to catch up on sleep...
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  2. #2
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by Nightfire View Post
    In class today, my teacher was going over a shortcut you can take in slope-intercept form working. Unfortuneately, i was half-dozing throughout the class, because i spent so much time yesterday working on social studies and language projects, and i had 2 hours of volunteer working, that i only got about 4 hours of sleep. Due to this, I have no clue how to do the shortcut. does anyone know of this shortcut, and how to work it?
    here's a couple problems from each category we're supposed to do...
    "Write the equation in slope-intercept form." (Note, we do not have to graph them.)
    4x+5y=15

    4x-y-3=0

    x-y=0

    "Decide whether the graphs of the two equations are parallel lines. Explain your answer."
    y=-3x+2; y+3x=-4

    2x-12=y; y=10+2x

    y+6x-8=0; 2y=12x-4

    thanks in advance. and dont worry, no more projects for a while, so i should be able to catch up on sleep...
    I'm not sure what the "shortcut" would be, but for your first three examples, simply solve for y. That automatically puts the equation into slope-intercept format.

    For the last three, two lines are parallel if their slopes are equal.

    -Dan
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  3. #3
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    That was the shortcut, as opposed to the book's ridiculous 4-6ish step method, involving working out the slope and graphing it...thanks
    haven't started on the parallels yet, but i'm sure i'll be able to do 'em now that i know what i'm looking for.
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  4. #4
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    Im also not sure of the shortcut you are seeking. Slope intercept form is y = mx + b where m is the slope of the line and b is the y-intercept.

    As top stated, in your first few equations, simply solve for y and you get slope intercept form and from there, the slope of the line and the y-intercept are easily found by observation.

    Ex.
    4x + 5y = 15
    5y = -4x + 15
    y = (-4/5)x + 3
    y = mx + b

    Here you can see the slope is -4/3 and the y-intercept is 3.
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