function y=ham1bien(x)
    %
    y = log(x.^2) + 2*x.^7 + 6;                % 3 nghiem
    %y = log(x.^2) + 2*x.^3 + 9;               % 3 nghiem
    %y = log(x.^2) + 4*x - 1;
    %y = 1/3*log(1*x.^3) + 4*x - 5;
    %y = 2*log(3*x.^4) + 4*x - 1;
    %y = 4*log(3*x.^4) + 2*x.^3 + 10;          % 3 nghiem
    %y = x.*log(3*x.^4) + 2*x - 5;             % 3 nghiem
    %y = 2*sin(2*x) + cos (3*x) + x^3 +10*x;
    %y = 3*sin(2*x) + cos (3*x) + x^3 +10;     % lap
    %y = x.*log(2*x.^6) + 3*x + 1;
    %y = log(5*x.^3) - x.^4 + 3*x.^2 +5;
    %y = exp(x) + 2*x + 13;
    %y = 1*log(x) - 2*x.^2 + 1*x.^4 - 42;
