Use the substitution u=1+exu = 1 + e^xu=1+ex to find
∫e3x1+ex dx\displaystyle\int \frac{e^{3x}}{1 + e^x}\,dx∫1+exe3xdx
363 exam-style questions on CCEA A Level Maths 3.6 Integration (A-level only), covering 3.6.1 Integration (A-level only), 3.6.2 Integration (A-level only), 3.6.3 Integration (A-level only), 3.6.4 Integration (A-level only), 3.6.5 Integration (A-level only), 3.6.6 Integration (A-level only), and 3.6.7 Integration (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.