Results 1 to 8 of 8

Math Help - Slope-intercept

  1. #1
    Junior Member
    Joined
    Mar 2012
    From
    United States
    Posts
    43

    Slope-intercept

    Problem states -
    Find the slope-intercept form of the equation of the line perpendicular to 4x+5y= -11, and containing the point (-7,6):

    I came up with y= - 4/5x + 2/5

    Is this right? I feel like the example I am following from the book is not the way the instructor was telling the class. I am not sure if I am even understanding the book example. I'm not sure if I am doing the right steps at all.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,329
    Thanks
    1244

    Re: Slope-intercept

    Quote Originally Posted by Kibbygirl View Post
    Problem states -
    Find the slope-intercept form of the equation of the line perpendicular to 4x+5y= -11, and containing the point (-7,6):

    I came up with y= - 4/5x + 2/5

    Is this right? I feel like the example I am following from the book is not the way the instructor was telling the class. I am not sure if I am even understanding the book example. I'm not sure if I am doing the right steps at all.
    How did you get 2/5 for the y intercept?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Mar 2012
    From
    United States
    Posts
    43

    Re: Slope-intercept

    I'm unsure if I did it right..
    I did:

    y-6= -4/5(x-[-7])
    y-6 = -4/5x - 28/5
    y= -4/5x - (-2/5)
    y= -4/5 + 2/5
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,329
    Thanks
    1244

    Re: Slope-intercept

    Quote Originally Posted by Kibbygirl View Post
    I'm unsure if I did it right..
    I did:

    y-6= -4/5(x-[-7])
    y-6 = -4/5x - 28/5
    y= -4/5x - (-2/5)
    y= -4/5 + 2/5
    It's easier to just transpose the equation of the line you have been given.

    \displaystyle \begin{align*} 4x + 5y &= -11 \\ 5y &= -4x - 11 \\ y &= \frac{-4}{5}x - \frac{11}{5} \end{align*}

    What are the gradient and the y-intercept?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Mar 2012
    From
    United States
    Posts
    43

    Re: Slope-intercept

    - 4/5 and 11/5?
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Senior Member
    Joined
    Mar 2012
    From
    Sheffield England
    Posts
    440
    Thanks
    76

    Re: Slope-intercept

    The gradient of the line you have been given is -4/5 so the line perpendicular to this has gradient +5/4. So you want the line with gradient +5/4 through the point (-7,6)
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Junior Member
    Joined
    Mar 2012
    From
    United States
    Posts
    43

    Re: Slope-intercept

    So would the final answer be y= 5/4x+2?
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Senior Member
    Joined
    Mar 2012
    From
    Sheffield England
    Posts
    440
    Thanks
    76

    Re: Slope-intercept

    Not +2. Line is y=5/4x+c. (-7,6) has to be on line. So we need 6=-35/4+c. So 59/4=c
    Line is y=5/4x+59/4
    Multiply both sides by 4
    4y=5x+59 (any other arrangement of this is OK)
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Slope and Y-intercept
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: September 8th 2009, 02:18 PM
  2. Slope AND y-intercept!!
    Posted in the Algebra Forum
    Replies: 1
    Last Post: February 11th 2008, 02:54 PM
  3. slope intercept
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: October 10th 2007, 01:15 PM
  4. slope-intercept
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: September 26th 2006, 11:11 PM
  5. Slope & Y-Intercept
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: March 28th 2005, 09:10 PM

Search Tags


/mathhelpforum @mathhelpforum