Integration by parts method.
Using integration by parts evaluate ∫x cos(3x) dx. Check your answer by taking the derivative.
Suppose the mass W of a worm grows according to the differential equation dW/dt = (4t - t2)e -3t with W(0) = 0. When does this worm grow fastest? Find W(2).
How much longer would the worm be at t = 2, if it always grew at the maximum rate? Use Integration by parts.