Question

If xy = 8, dx/dt = 2, find dy/dt when x = 3.

The more detailed the explanation the better.
Thanks in advance!!!

Answer 1

Dt(xy) = x'y + xy'

xy = 8 implies y = 8/x if i see it right


hence y' = -8/x^2

Answer 2

im sure theres an idea brewing in this someplace :)

Answer 3

hence y' = -8x'/x^2 forgot that x wasnt a fucntion of itself

Answer 4

I think hamidaarab has come up with something

Answer 5

then x=3; y = 8/3 if we are to keep the .. i spose he diesnt know that the posts are meant to be responded to inside of them ...

Answer 6

xy = 8, dx/dt = 2, find dy/dt when x = 3.
picking up amistre's
x'y + xy'= 0
sub in x'= 2, x=3 , y= 8/x = 8/3
2*8/3 + 3 y'= 0
solve for y'

Answer 7

thanks!