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!

Homework Help: Im trying to determine the y and x intercepts of this line.

  1. Apr 20, 2016 #1
    1. The problem statement, all variables and given/known data
    I am trying to determine the x- and y-intercepts of the line 3x – 5y + 15 = 0.

    2. Relevant equations
    standard form

    3. The attempt at a solution:

    To find the x-intercept (where the line crosses the x-axis), substitute 0 in for y:
    3x + 5y + 15 = 0 (substituted 0 in for y)
    3x + 5(0) + 15 = 0 (multiply 5 by 0)
    3x + 15 = 0 (Next ,subtract 15 from both sides)
    3x = -15 (divided both sides by 3)
    x = -5
    x-intercept = -5.

    I will use this method to solve for the y-intercept.

    To find the y-intercept (where the line crosses the y-axis), substitute 0 in for x:
    3x + 5y + 15 = 0 (substituted 0 in for x)
    3(0) + 5y + 15 = 0 (multiply 3 by 0)
    5y + 15 = 0 (Next ,subtract 15 from both sides)
    5y = -15 (divided both sides by 5)
    y = -3
    y-intercept = -3

    I'm pretty sure I did it correct but i just want to be sure I understand what I'm doing and answering it correctly. Also can you guys tell me if my way is like clear, as in you can understand it. Thx alot :)
  2. jcsd
  3. Apr 20, 2016 #2


    User Avatar
    Homework Helper

    It seems correct, but why do you substitute? Do you understand that?
  4. Apr 20, 2016 #3
    Sorry what do you mean by bold?
  5. Apr 20, 2016 #4


    User Avatar
    Homework Helper

    Nothing, was just a code error. Could you answer the question so I can see whether you understand why you can do this to solve the exercice?
  6. Apr 20, 2016 #5
    Well my dad kinda just taught me this way, so you would try to isolate the variable y( you can start with x but im starting with y). so to isolate the variable i have to move some values to the other side of the equations. I searched online and it said i should substitute the variable y for 0. I don't know why but i did ( my dad didnt tell me to do that i did it on my own). So I did and continue the way my dad taught me and got my final result.
  7. Apr 20, 2016 #6


    User Avatar
    Homework Helper

    Wel you can consider it this way. The y-axe has equation: x = 0, so this are all the points with x coordinate 0. You want to know where your line intersects with the y-axis, and you know that the x-coordinate should be 0. Since you say x = 0 in the equation, you will automatically get the y value corresponding with this x-value. Is this clear? (I need to go to school now btw, so I won't reply for a couple of hours)
  8. Apr 20, 2016 #7
    Wow that really helps thanks alot ill keep that in mind while i answer my next problem :)

    thx you !!!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted