1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

* Easy Linear Question. Slope and y intercept. Thanks!

  1. Sep 16, 2010 #1
    1. The problem statement, all variables and given/known data

    Determine the slope and y-intercept of the line: 1/2y = x - 1 - Graph the line

    2. Relevant equations

    I know this is a simple one, but im having troubles with it. Can someone lay out how they got the slope, and then how they got the y-intercept. pointing out the steps ?

    3. The attempt at a solution

    I can't figure out how to get the slope. I must be just missing a major step lol.

  2. jcsd
  3. Sep 16, 2010 #2


    User Avatar
    Homework Helper

    You need to put the form in the equation y=mx+c, 'm' is the gradient and 'c' is the y-intercept.

    So try multiplying by some number to get it into that form.
  4. Sep 16, 2010 #3
    First off, what do I do about the 1/2y ?
  5. Sep 16, 2010 #4


    User Avatar
    Homework Helper

    Wait a minute. What is the original equation? Is it this:
    [tex]\frac{1}{2y} = x - 1[/tex]
    or this?
    [tex]\frac{1}{2}y = x - 1[/tex]

    It looks like rock.freak667 is assuming the later. (By the way, you have to be careful when typing in equations. Either learn LaTex or use parentheses.) You want to isolate the y. As he/she said, you multiply both sides of the equation by some number to get the y by itself on the left side. So, what do you do?

  6. Sep 16, 2010 #5
    [tex]\frac{1}{2}y = x - 1[/tex]

  7. Sep 16, 2010 #6


    User Avatar
    Science Advisor

    RockFreak667 assume the OP meant [itex](1/2)y= x- 1[/itex] because [itex]\frac{1}{2y}= x- 1[/itex] is not a line and doesn't have a "slope"!

    To solve for y, multiply both sides by 2. Once you have it in the form y= mx+ b, m is the slope and b is the y-intercept.
  8. Sep 16, 2010 #7
    why do I divide both sides by 2? where did u get 2 from?
  9. Sep 16, 2010 #8


    User Avatar
    Homework Helper

    if you have 0.5y=x-1, how would you get 'y' only on the left side? Multiply by 2 right?
  10. Sep 16, 2010 #9
    Just so I get the steps right.

    Why pick 2?

    And you say multiply both sides by 2. So, can u break that down? How does that become:
    y = 2(x -1)

    Appreciate it!
  11. Sep 16, 2010 #10


    User Avatar
    Homework Helper

    (1/2)y= (x-1)

    multiply by 2

  12. Sep 16, 2010 #11


    User Avatar
    Homework Helper

    Oh, I know. I was being difficult on purpose.

    You pick 2 because 2 is the reciprocal of 1/2. When you multiply (1/2)y by 2, the 1/2 and 2 "cancel each other out," leaving with the y by itself. If I have another linear equation like
    [tex]\frac{1}{6}x = 4[/tex]
    the reciprocal of 1/6 is 6, so I multiply both sides by 6 to isolate the x:
    6 \cdot \frac{1}{6}x &= 6 \cdot 4 \\
    x &= 24

    One more thing:
    This is not yet in slope-intercept form, y = mx + b. You still have one more thing to do.

    Last edited: Sep 16, 2010
  13. Sep 16, 2010 #12
    What is left to do? Just take out the bracket, so it becomes:

    y = 2x -1
  14. Sep 17, 2010 #13


    User Avatar
    Homework Helper

    No, you can't just "take out the bracket." You have to apply the distributive property:
    a(b + c) = ab + ac

  15. Oct 5, 2010 #14
  16. Oct 6, 2010 #15


    Staff: Mentor

    If you mean y = 2x - 1/2, no.
    You had y = 2(x - 1). If you expand the right side as eumyang suggested, what do you get?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook