Partial Derivatives With N-Variables

TranscendArcu
Messages
277
Reaction score
0

Homework Statement



Given F(x_1,x_2,...,x_i,...,x_n) = nth-root(x_1*x_2*...*x_i*...*x_n), how do I take the partial derivative with respect to x_i, where x_i is an arbitrary variable?

Homework Equations


The Attempt at a Solution



Would it just be:

(1/n)(x_1*x_2*...*x_i*...*x_n)^((1/n)-1)*(x_1*x_2*...*x_i-1*x_i+1*...*x_n)?
 
Physics news on Phys.org
You got it!
 
Alright, nice!

What I'd like to try to do with this problem is maximize F (the equation for the geometric mean) when it is constrained by G(x_1,x_2,...,x_n) = x_1 + x_2 + ... + x_n = c, where c is some constant. I can take the partial derivative of G with respect to x_i and get,

G_x_i = 1

But I don't really know if I am a) on the right track for this problem or b) how to proceed if I am on the right track. What should my next step be?
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top