I'm stuck on this problem for the past hour. I've tried solving for all variables and none of the steps I'm doing are getting me to the right answer. Find the point on sphere x^2+y^2+z^2=25 farthest from point (1,1,-1). My steps: http://i.imgur.com/c5kUj9g.png Correct Answer: x= -5/sqrt(3) y= -5/sqrt(3) z= 5/sqrt(3) Thanks in advance. EDIT: On the part where I set negative lambda equal to "...", I made x=y to make solving for "z" easier since x and y are symmetrical.