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

    10
    ReputationRep:
    I've been given the equation:

    A=600x-24x^2

    I found dA/dx=-48x+600

    and it says find d^2A/dx^2, which I find to = -48.

    It wants to plug the stationary value (600/48) into it to determine its nature. I can't because there's no x in the second derivative. Any help is greatly appreciated, thanks

    Edit:Title should read I found the second derivitave but I cant do the rest
    Offline

    0
    ReputationRep:
    doesn't that mean that the second derivative is -48, which is < 0 and so it is a maximum?
    Offline

    0
    ReputationRep:
    When x=(600/48), what is the value of the second derivative? (hint: just state the value, it is independent of x)
    Offline

    0
    ReputationRep:
    What do you mean by "determine its nature"?

    Anyhow, just look at it this way: for any given value of x, the slope will be -48. The x quite literally does not matter.
    • Thread Starter
    Offline

    10
    ReputationRep:
    What do you mean by "determine its nature"?
    determine whether its a minimum(>0), maximum(<0) or point of inflection(=0)

    and yeah, it says find the value of d^2A/dx^2, so the value being -48, its <0 so its a maximum, Thanks
 
 
 
  • 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 rather give up salt or pepper?
    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

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