Question

How do I do 1(a)? Please help, urgent!

Answer 1

3n² + 8n

Explanation:

∑ (5 + 6r )

= ∑ 5 + 6 ∑ r

= 5n + 6 ×
`(1)/(2)` n(n + 1)

= 5n + 3n(n + 1)

= 5n + 3n² + 3n

= 3n² + 8n