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Math Help - Write linear equation in functional natation

  1. #1
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    Write linear equation in functional natation

    Hey guys,

    could somebody please check if the following is right?

    Task: Write the linear equation 4x -9y = -45 in functional notation, and determine the x-and y-intercepts. Show your work using functional notation.

    My work:

    4x -9y = -45 is
    -9y = -4x -45 is
    y = -4/-9 x +5 is

    f(x) = -4/-9 x +5

    The x-intercept is where y=0
    0 = -4/-9 x +5
    -5 = -4/-9 x
    x = -11.25

    The y-intercept is where x=0
    f(0) = -4/-9 (0) +5
    f(0) = 0 +5
    f(0) = 5

    Is my whole work right or is there any mistake? Thank you.
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  2. #2
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    Re: Write linear equation in functional natation

    Quote Originally Posted by ford2008 View Post
    Task: Write the linear equation 4x -9y = -45 in functional notation, and determine the x-and y-intercepts. Show your work using functional notation.
    f(x)=\frac{4}{9}x+5.
    Thanks from ford2008 and HallsofIvy
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  3. #3
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    Re: Write linear equation in functional natation

    Quote Originally Posted by ford2008 View Post
    Hey guys,

    could somebody please check if the following is right?

    Task: Write the linear equation 4x -9y = -45 in functional notation, and determine the x-and y-intercepts. Show your work using functional notation.

    My work:

    4x -9y = -45 is
    -9y = -4x -45 is
    y = -4/-9 x +5 is
    -4/-9= 4/9 but you seem to recognize that later so it is just awkwardly written, not an error.

    f(x) = -4/-9 x +5

    The x-intercept is where y=0
    0 = -4/-9 x +5
    -5 = -4/-9 x
    x = -11.25

    The y-intercept is where x=0
    f(0) = -4/-9 (0) +5
    f(0) = 0 +5
    f(0) = 5

    Is my whole work right or is there any mistake? Thank you.
    Yes, those are correct.

    I realize you were told to "Write the linear equation 4x -9y = -45 in functional notation" but, frankly, it would have been simpler to use the original form.
    With 4x -9y = -45, setting y to 0 gives 4x= -45 so that x= -45/4= -11.25 is the x-intercept. Setting x= 0, -9y= -45 so that y= 5 is the y intercept.
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