Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    20
    ReputationRep:
    Dear Maths Genius,

    I am writing because i have a problem with drawing modulus functions on the same graph. When you look at the question, I try to draw the functions as accurately as I can but i still miss out one intersection point.

    I have attached the pictures to the question I did in the edexcel and the mistake I made. Please i want to know if there are anhy tips on how to draw the functions probably without missing out any points of intersections.

    Thank you very much.

    Name:  mod q .jpg
Views: 106
Size:  99.5 KBAttachment 567786567788 Attachment 567786567788
    Attached Images
      
    • Community Assistant
    • Welcome Squad
    Offline

    20
    ReputationRep:
    Community Assistant
    Welcome Squad
    (Original post by bigmansouf)
    ...
    You can find all the points of intersection by realising that \lvert x\rvert = \lvert -4x-5 \rvert \rightarrow \pm x=\pm(-4x-5) which gives you 4 linear equations to solve:
    x=(-4x-5) ... (1)
    x=-(-4x-5) ... (2)
    -x=(-4x-5) ... (3)
    -x=-(-4x-5) ... (4)

    but you may notice that (1)=(4) and (2)=(3) which leaves you only with 2 equations to solve therefore this shows that for any two moduli of two linear functions there can be a maximum of 2 intersections.

    Once you have the intersections, along with where the minimum points, you can work from there to draw them. However also take into account the gradients which can help you draw the graphs accurately together, as one will have steeper lines than the other.
    Offline

    15
    ReputationRep:
    For x>-5/4 you have sketched y=4x+5 as having a lower gradient than y=x which of course is not true.
    • Thread Starter
    Offline

    20
    ReputationRep:
    (Original post by RDKGames)
    You can find all the points of intersection by realising that \lvert x\rvert = \lvert -4x-5 \rvert \rightarrow \pm x=\pm(-4x-5) which gives you 4 linear equations to solve:
    x=(-4x-5) ... (1)
    x=-(-4x-5) ... (2)
    -x=(-4x-5) ... (3)
    -x=-(-4x-5) ... (4)

    but you may notice that (1)=(4) and (2)=(3) which leaves you only with 2 equations to solve therefore this shows that for any two moduli of two linear functions there can be a maximum of 2 intersections.

    Once you have the intersections, along with where the minimum points, you can work from there to draw them. However also take into account the gradients which can help you draw the graphs accurately together, as one will have steeper lines than the other.
    Thank you very much for helping me

    Im sorry i cant rep you as it will not allow me
    • Thread Starter
    Offline

    20
    ReputationRep:
    (Original post by B_9710)
    For x>-5/4 you have sketched y=4x+5 as having a lower gradient than y=x which of course is not true.
    thank you
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Would you like to hibernate through the winter months?
    Useful resources

    Make your revision easier

    Maths

    Maths Forum posting guidelines

    Not sure where to post? Read the updated guidelines here

    Equations

    How to use LaTex

    Writing equations the easy way

    Student revising

    Study habits of A* students

    Top tips from students who have already aced their exams

    Study Planner

    Create your own Study Planner

    Never miss a deadline again

    Polling station sign

    Thinking about a maths degree?

    Chat with other maths applicants

    Can you help? Study help unanswered threads

    Groups associated with this forum:

    View associated groups
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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

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