Question

I need help with this, please. Any advice would be appreciated.

Answer 1

125

Explanation:

Answer 2

see explanation

Explanation:

The sum to n terms of an arithmetic sequence is

`S_(n)` =
`(n)/(2)` [ 2a₁ + (n - 1)d ]

where a₁ is the initial value and d the common difference

Given

`S_(n)` =
`(n)/(2)` [ 10 + (n - 1)3 ]

Then by comparison

2a₁ = 10 ( divide both sides by 2 )

a₁ = 4 ← initial value

and d = 3 ← common difference

Thus

`S_(8)` =
`(8)/(2)` [ 10 + (7 × 3) ]

= 4(10 + 21)

= 4 × 31

= 124