令√(3x+9)=u,则:3x+9=u^2,∴3dx=2udu,∴dx=(2/3)udu.
∴∫[e^√(3x+9)]dx
=(2/3)∫ue^udu=(2/3)∫ud(e^u)=(2/3)ue^u-(2/3)∫(e^u)du
=(2/3)√(3x+9)e^√(3x+9)-(2/3)e^u+C
=(2/3)√(3x+9)e^√(3x+9)-(2/3)e^√(3x+9)+C
令√(3x+9)=u,则:3x+9=u^2,∴3dx=2udu,∴dx=(2/3)udu.
∴∫[e^√(3x+9)]dx
=(2/3)∫ue^udu=(2/3)∫ud(e^u)=(2/3)ue^u-(2/3)∫(e^u)du
=(2/3)√(3x+9)e^√(3x+9)-(2/3)e^u+C
=(2/3)√(3x+9)e^√(3x+9)-(2/3)e^√(3x+9)+C