Hey! Sign in to get help with your study questionsNew here? Join for free to post

Lines and gradients

Announcements Posted on
Would YOU be put off a uni with a high crime rate? First 50 to have their say get a £5 Amazon voucher! 27-10-2016
    • Thread Starter

    If I have the gradient and a point the line passes through then how do I work out where the line crosses the y axis?

    the equation of a line is y=mx+c
    the gradient will give you the m, so for example if the gradient is 4 your equation is now y=4x+c
    then you input the point into the equation so for example if you has (2,3) your equation would now be 3=4x2+c
    you then solve this to find c --> c=3-(4x2) ---> c=-5
    because c is the y intersect you now know the line crosses the y axis at -5

    (Original post by libbydavis)
    If I have the gradient and a point the line passes through then how do I work out where the line crosses the y axis?
    Every straight line has the equation: y = mx + c
    (where m is the gradient and c is the y-intercept)

    You have been given the gradient so substitute this value in for m.

    Using the point that they have given you, substitute in the values of y and x, and then rearrange the equation to work out c.

    Form the equation for your line using y = m(given)x + c(what you worked out)

    When a line crosses the y axis, x will always be 0. So substitute x = 0 into the equation you made and you will be able to find c.

    For example:

    "a line with a gradient of 3 passes through the point (5,7). Find out its y-intercept" (I just made this up lol)

    y = mx + c
    y = 3x + c
    7 = 15 + c
    c = -8
    y = 3x - 8

    when x = 0:
    y = 0 - 8
    y = -8
Write a reply…


Submit reply


Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: May 11, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

I want...
Useful resources

Study tools


Essay expert

Learn to write like a pro with our ultimate essay guide.

Thinking about uni already?

Thinking about uni already?

See where you can apply with our uni match tool

Student chat

Ask a question

Chat to other GCSE students and get your study questions answered.


Make study resources

Create all the resources you need to get the grades.


Create your own Study Plan

Organise all your homework and exams so you never miss another deadline.

Resources by subject

From flashcards to mind maps; there's everything you need for all of your GCSE subjects.


Find past papers

100s of GCSE past papers for all your subjects at your fingertips.

Help out other students

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.