Hey there! Sign in to join this conversationNew here? Join for free

help with maths...am I just being really stupid?? Watch

    • Thread Starter
    Offline

    0
    ReputationRep:
    Okay so I'm just working through the OCR Core 3 maths specimen paper, and to find the area under a curve I have to integrate (4x+1)^-1/2

    Now I thought this would work out as 1/4 x 1/2(4x+1)^1/2 and therefore 1/8(4x+1)^1/2

    But the answer scheme has it down as being 1/2(4x+1)^1/2

    Is the answer scheme wrong or am I just being really thick? I am majorly hungover from a night out last night so the latter wouldn't surprise me tbh.

    But I am aware that the specimen papers and answer schemes aren't as vigorously checked as real papers, so it is possible it's wrong.

    Help is appreciated
    Offline

    1
    ReputationRep:
    Differentiate your answer and the mark scheme's answer, and you'll see the mistake you've made.
    • Thread Starter
    Offline

    0
    ReputationRep:
    Ohh yh I know what i did...I multiplied by the new power rather than the inverse. Thanks
    Offline

    0
    ReputationRep:
    (Original post by alexKS)
    Okay so I'm just working through the OCR Core 3 maths specimen paper, and to find the area under a curve I have to integrate (4x+1)^-1/2

    Now I thought this would work out as 1/4 x 1/2(4x+1)^1/2 and therefore 1/8(4x+1)^1/2

    But the answer scheme has it down as being 1/2(4x+1)^1/2

    Is the answer scheme wrong or am I just being really thick? I am majorly hungover from a night out last night so the latter wouldn't surprise me tbh.

    But I am aware that the specimen papers and answer schemes aren't as vigorously checked as real papers, so it is possible it's wrong.

    Help is appreciated
    If y=(4x+1)^1/2
    so dy/dx=(1/2)*4*(4x+1)^(-1/2)=2(4x+1)^-1/2
    So the integral of (4x+1)^-1/2 must be 1/2(4x+1)^1/2
 
 
 
  • 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
    What newspaper do you read/prefer?
    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.