stuart clark

Finding $\displaystyle \mathop{\sum\sum\sum}_{1\leq i<j<k\leq n}ijk$

Cho $x^2+y^2+z^2=1.$ Tim Max $(3\sqrt{2}y-\sqrt{11}z)^2+(\sqrt{7}z-3\sqrt{2}x)^2+(\sqrt{11}x-\sqrt{7}y)^2$ 

Cho $x,y,z,t>0,$ Tim Min $x^5+3\sqrt{3}\; y^5+\sqrt{3}z^5+t^5-15xyzt$