function S=test7(x)
% Powell, 1964
% x0 = [-3, -1, 0, 1]'
% xo = [0, 0, 0, 0]'
% S(xo) = 0
%
% Hessiana e´ singular no minimo

S=(x(1)+10*x(2)).^2+5*(x(3)-x(4)).^2+(x(2)-2*x(3)).^4+10*(x(1)-x(4)).^4;
