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-   -   Find the maximum rate of change (http://www.physicsforums.com/showthread.php?t=576057)

andyk23 Feb9-12 08:01 PM

Find the maximum rate of change
 
Find the maximum rate of change of the function f(x,y) = (3 y^5)/x at the point (1,2)

First I took the gradient of f(x,y)=<-3y^5*x^-2,15y^4*x^-1>
and took the pt <1/sqrt(5),2/sqrt(5)>
Then <-3y^5*x^-2,15y^4*x^-1>*<1/sqrt(5),2/sqrt(5)>
the answer i get is 171.73
I'm not sure where my error is

SammyS Feb9-12 08:19 PM

Re: Find the maximum rate of change
 
Quote:

Quote by andyk23 (Post 3755623)
Find the maximum rate of change of the function f(x,y) = (3 y^5)/x at the point (1,2)

First I took the gradient of f(x,y)=<-3y^5*x^-2,15y^4*x^-1>
and took the pt <1/sqrt(5),2/sqrt(5)>
Then <-3y^5*x^-2,15y^4*x^-1>*<1/sqrt(5),2/sqrt(5)>
the answer i get is 171.73
I'm not sure where my error is

Why not evaluate the gradient at the point (1, 2) ?

andyk23 Feb9-12 08:24 PM

Re: Find the maximum rate of change
 
Sorry I evaluated at the gradient(1,2)=<-96,240> and then <-96,240>*<1/sqrt(5),2/sqrt(5)>


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