This is a function from R^3 -> R. Find the Jacobian, (a 1x3 matrix, gradient). See if (x,y,z) = (60,60,60) is a critical point. then find the Hessian (the matrix of second order partial derivatives.), then use the second partial derivative test.
Last edited by MacstersUndead; Aug 25th 2010 at 09:31 PM.