kill(all)$

van=facebook.com/LearningCalculus$

red(x):=x*(x+1)$

create_list(red(x),x,1,14);

W:sum(red(x),x,1,14);

grn(x):= rhs(sum(red(u),u,1,x)=x^3/3+x^2+(2*x)/3);

grn(14);

blu(x):=rhs('integrate(red(x),x)=
          ''(integrate(expand(red(x)),x)+C));