Thread: extremely hard partial derivative question

thanks for the helppp

Originally Posted by goaway716

If f_x and f_y are the partial derivatives of f(x,y) and f_s and f_t are the partial derivatives of f viewed as a function of s and t, show that if:

s=(x^3)-(3xy²)

t=3x²y-y^3

then

xf_x+yf_y=3(sf_s+tf_t)

please help me finishing this problem as i got no clue how to go about it
thanx

You need to use the chain rule.





Then just calculate

and simplify and sub out x's and y's for s's and t's.

i have a question and i make a half of it but it is really hard, i had try so many times but did not get the answer.., please help me to find the answer., sorry for my bad english..IMG.pdf.., only number 1 but ignore du/dx+dv/dy=0.., because i already prove it...