Question 3 - A-Level Maths

Exam Board	AQA
Module	FP1 (Further Pure Mathematics 1)
Year	2006
Session	June
Topic	Sequences and series, recurrence and convergence

3 Show that $$\sum _ { r = 1 } ^ { n } \left( r ^ { 2 } - r \right) = k n ( n + 1 ) ( n - 1 )$$ where $k$ is a rational number.