This IB Maths AA SL Topic SL 5.2 – Increasing and Decreasing Functions resource develops students’ understanding of how the sign of the derivative describes the behaviour of a function. Students learn that a function is increasing where (f’(x)>0), decreasing where (f’(x)<0), and constant where (f’(x)=0), supported by clear graphical explanations and derivative notation.

The lesson then applies these ideas to finding critical and stationary points and determining intervals of increase and decrease using sign tables and test values. Practice includes algebraic and graphical problems, as well as a contextual marginal-cost application, with fully worked solutions to help students interpret derivatives and analyse function behaviour confidently.