Re: Differentiation problem
I can't help with the first bit, the the simplification:
-p^(-1/4 - 3/4) * q^(3/4 - -1/4) = -p^(-1) * q^(1) = -q/p
Re: Differentiation problem
By the chain rule, dU/dx2*dx2/dx1 = dU/dx1, so
dx2/dx1 = (dU/dx1) / (dU/dx2)
From the product rule and partial differentiation we get
dU/dx1 = (x2)^(3/4)*(3/4)*(x1)^(-1/4)
dU/dx2 = (x1)^(3/4)*(3/4)*(x2)^(-1/4)
Substituting these into the formula above, we find
dx2/dx1 =
(x2)^(3/4)*(3/4)*(x1)^(-1/4)
----------------------------
(x1)^(3/4)*(3/4)*(x2)^(-1/4)
= x2/x1.
This should be the right answer barring algebraic mistakes, and I'm pretty sure it's the same general approach you used because of the similarity between this and your q/p formula.
Re: Differentiation problem
Yeah that's what I got. Thanks a lot.