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Slope Intercept Form?

Next, find the equation of the line that passes through the points (1,8) and (4,4). Enter exact answers only (no approximations), and write the equation in slope-intercept form (y=mx+b) if possible.

would it be y-8=-4/3(1)+b?

2 Answers

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  • ?
    Lv 7
    2 months ago

    Slope intercept form is

    y = mx + b

    ---------------------

    Use the two points to find the slope, m

    m = rise/run

    m = ∆y / ∆x

    m = (y₂ - y₁) / (x₂ - x₁)

    m = (4 - 8) / (4 - 1)

    m = -4/3

    ----------------------

    to find "b" use m = -4/3 and either point

    using point (1, 8)

    y = mx + b

    8 = (-4/3)(1) + b

    Convert to 3rds

    24/3 = -4/3 + b

    Ad 4/3 to both sides

    28/3 = b

    -------------------------

    Using m = -4/3 and b = 28/3 the slope intercept equation can be writen

    y = (-4/3)x + 28/3 <––––––

     

    Attachment image
  • Alan
    Lv 7
    2 months ago

    No,  your equation must include an x term    

    slope = (4-8) / ( 4-1) = -4/3   

    to find b 

    yes,  

    y = (-4/3)x +b 

    b = y  + (4/3)x     = 8  + (4/3)*1 =   24/3  + 4/3 = 28/3  

    y = (-4/3)x  +   28/3  

    so if you try to use point slope form .     

    (y -8)  =  (-4/3) (x  -1)  

    y- 8 = (-4/3)x    + 4/3 

    y = (-4/3)x   + 8 + 4/3    

    Gives the same answer in slope intercept form  

    y = (-4/3)x   +   28/3      

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