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Thread: Finding the slope of a line

  1. #1
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    Finding the slope of a line

    We just started doing inequalities in class and I get the basics, but this is what gets me.

    M = 7, point (0,-5)

    How would I write this in Y = mx + b format?
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  2. #2
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    $\displaystyle y = m * x + b$
    First, we know m:

    $\displaystyle y = 7 * x + b$

    Next, we know x and y:

    $\displaystyle -5 = 7 * 0 + b$

    Solve for b:

    $\displaystyle -5 = b$

    Notice, if $\displaystyle x = 0$, and $\displaystyle (x,y)$ is on the line, $\displaystyle b = y$.

    So, now, write your equation down:

    $\displaystyle y = 7 * x + -5$

    Or:

    $\displaystyle y = 7 * x - 5$
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  3. #3
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    Quote Originally Posted by largebabies View Post
    We just started doing inequalities in class and I get the basics, but this is what gets me.

    M = 7, point (0,-5)

    How would I write this in Y = mx + b format?
    The y intercept = -5, therefore

    y=7x-5
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  4. #4
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    m=7, (0,-5)


    y- (-5)
    _______ = 7 : then cross multiply
    x-0


    y+5= 7x: move five to the other side by subtracting it

    so then you get y=7x -5
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  5. #5
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    Thank you all, it's help alot

    Although, I need help on another equation, what if there is two points?

    example: M = 3/2, point (5,-6)?
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  6. #6
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    $\displaystyle y = m * x + b$
    First, we know m:

    $\displaystyle y = \frac 3 2 * x + b$

    Next, we know x and y:

    $\displaystyle -6 = \frac 3 2 * 5 + b$

    Solve for b:

    $\displaystyle -6 - \frac {15} 2 = \frac {-27} 2 = b$

    So, now, write your equation down:

    $\displaystyle y = \frac 3 2 * x + \frac {-27} 2$
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  7. #7
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    Thank you once again, although it's supposed to be 27/2 not -27/2
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  8. #8
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    Alright, how about this?

    "passes through (4,2) and (0,8)"
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  9. #9
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    Quote Originally Posted by largebabies View Post
    Alright, how about this?

    "passes through (4,2) and (0,8)"
    Find the slope:

    $\displaystyle m=\frac{y_1-y_2}{x_2-x_1}=\frac{8-2}{0-4}=\frac{6}{-4}=-\frac{3}{2}$

    From (0, 8) we know the y-intersept = 8.

    Use the slope-intercept form of the general equation:

    $\displaystyle y=mx+b$, where m is the slope, and b is the y-intercept.

    $\displaystyle y=-\frac{3}{2}x+8$
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  10. #10
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    Unhappy

    that helped alot!

    although i'm now stuck on another equation , I did the same thing with this and got y= -10/-2 when I needed -5/4.

    The equation goes like this.

    “passes through (-5,10) and (3,0)”

    help?
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