function S=test9(x)
% Himmelblau, 1972
% x0 = [1, 1]'
% xo = [3, 2]', xo = [3.58443, -1.84813]', xo = [-3.7793, -3.2832]' e xo = [-2.8051, 3.1313]'
% S(xo) = 0
% local maximum: xo = [-0.2708, -0.9230]', S(xo) = 181.6

S=(x(1).^2+x(2)-11).^2+(x(1)+x(2).^2-7).^2;
