∫ e^(2x) dx= ∫ e^(2x) d(2x/2)= (1/2)∫ e^(2x) d(2x)= (1/2)e^(2x) + C或令u = 2x,du = 2dx => dx = (1/2)du∫ e^(2x) dx= ∫ e^u * (1/2)du= (1/2)e^u + C= (1/2)e^(2x) + C