Edexcel FP1 — Question 5

Exam BoardEdexcel
ModuleFP1 (Further Pure Mathematics 1)
TopicProof by induction

5. Prove that $$\sum _ { r = 1 } ^ { n } 6 \left( r ^ { 2 } - 1 \right) \equiv ( n - 1 ) n ( 2 n + 5 )$$