kill(all)$
van=facebook.com/LearningCalculus$

f(t):=t;

A(x):=integrate(1*f(t),t,0,x);
B(x):=integrate(t*f(t),t,0,x);

A;

y(x):=fullratsimp(%e^x-1-B+(x-1)*A)$
y(x);

y(3);