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

    Show that:
     x \frac {\partial f}{\partial x} + y \frac{\partial f}{\partial y} = 2v \frac {\partial f}{\partial v}
     v= x^2+y^2
    Any ideas what should I do? I tried using basic chain rule, but to na avail
     \frac {\partial f}{\partial v} = \frac {\partial f}{\partial x} \frac {\partial x}{\partial v} + \frac {\partial f}{\partial y} \frac {\partial y}{\partial v}
    I feel like I'm missing something, or my chain rule is incorrect.
    • PS Helper

    PS Helper
    I think you're just going about it the wrong way. Write \dfrac{\partial f}{\partial x} in terms of \dfrac{\partial f}{\partial v} and so on, and then it all comes out.
    • Thread Starter

    Yep, that was stupid ;p
    I messed up the chain rule when I was trying to do it the other way around. I took me half an hour to find that mistake. Congratz to me.
Do you agree with the PM's proposal to cut tuition fees for some courses?
Useful resources

Make your revision easier


Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here


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