A-Level Maths Edexcel (9MA0)

Locate roots of $f(x) = 0$ by considering changes of sign of $f(x)$ in an interval of $x$ on which $f(x)$ is sufficiently well behaved.

Students should know that sign change is appropriate for continuous functions in a small interval.

Understand how change of sign methods can fail.

When the interval is too large sign may not change as there may be an even number of roots.

If the function is not continuous, sign may change but there may be an asymptote (not a root).