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

    1
    ReputationRep:
    You are given that x=y^2 + 4
    i) Find dy/dx in terms of y.
    ii) Rearrange x=y^2 + 4 in the form y=g(x)
    iii) Differentiate y=g(x) to find dy/dx in terms of x.
    iv) Show that dy/dx * dx/dy =1
    v) For what values of x are your answers valid.

    I have done the first four parts but not sure about last two, help would be appreciated
    Offline

    5
    ReputationRep:
    For part 4 just look at your answers to past 1 and 2. If you multiply them together you should get 1.

    2y * 1/2y = 2y/2y = 1


    Then for part 5 I'm not quite sure which bit they are asking for, but...

    when x = y^2 + 4, x ε ℝ (meaning x is any real number)
    - this is because you can square any real number (including negatives) and add 4 to any real number (including 0)

    when y = (x-4)^1/2, x ≠ 4
    - this is because of x was 4 then the bracket would equal 0, and doing 0 to the power of -1/2 results in a math error
    • Thread Starter
    Offline

    1
    ReputationRep:
    Thank you very much!
 
 
 
Poll
Who is your favourite TV detective?
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

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.