Calculus Calculus Math Forum

 November 16th, 2008, 12:27 PM #1 Newbie   Joined: Nov 2008 Posts: 1 Thanks: 0 Lagrange Multiplier Fix.. Hi, I'm in the midst of revision for a calculus exam next week. I'm not sure if I tackled this problem correctly. Find the maximum and minimum distances from the origin for points on the curve described by 3x^2 + 2y^2 + z^2 = 20 and z^2 = 2xy . I know the constraint eqns defined by g(x,y,z)= 3x^2 + 2y^2 + z^2 - 20 = 0 and h(x,y,z)= z^2 = 2xy Also I define the function f(x,y,z)= x^2 + y^2 + z^2, which I have to find the minimum and maximum values for. In short, what I did was to introduce a function F(x,y,z,k,j) = f(x,y,z) - k[g(x,y,z)] - j[h(x,y,z)] and solve for grad(F)=0 ( k and j are constants) The problem is when I realised 1 of the constants I had used turns out to be 0, is that correct? PLEASE, would really appreciate some guidance on this: my ans is minimum: (-sqrt(13/ , 0, 0) and max: (sqrt(13/ , 0, 0) Will be glad to countercheck with some of your answers  Tags fix, lagrange, multiplier Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post MMCS Calculus 3 December 7th, 2013 08:44 AM Brazen Calculus 1 January 15th, 2013 11:29 AM trey01 Applied Math 2 March 25th, 2012 08:14 AM dk1702 Abstract Algebra 1 July 21st, 2010 06:25 AM OSearcy4 Calculus 2 October 16th, 2009 02:44 PM

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