Use the substitution u=1+exu = 1 + e^xu=1+ex to find ∫e3x1+exdx\displaystyle \int \frac{e^{3x}}{1 + e^x} dx∫1+exe3xdx
119 exam-style questions on CCEA A Level Maths 3.6.4 Integration (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.