implicit differentiation

y³ + xy = 4x - 2

I understand that to differentiate y³ I would get 3y² dy/dx but how do I do xy? It's on a practise paper I'm doing and I can't seem to work out where the answer comes from. Thanks x

Reply 1

m:)ckel

To do d/dx[xy] you have to use product rule. You get:

(1)(y) + (dy/dx)(x) = y + x(dy/dx)

(differentiate the first term, times by the other etc...)

Reply 2

Spenceman_

think of it as a product of two functions and differentiate is as such.

d(xy)/dx = x(dy/dx) + y

Reply 3

rachplatt

Thanks a lot :-) I did know that, I just have my p5 paper tomorrow and I've had 4 modules of exams already this week and I'm too tired to think, but I need to revise! Sorry for asking a silly question!