Question

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

Answer 1

Answer:

see explanation

Step-by-step explanation:

The sum to n terms of an arithmetic sequence is

$S_{n}$ = $\frac{n}{2}$ [ 2a₁ + (n - 1)d ]

where a₁ is the initial value and d the common difference

Given

$S_{n}$ = $\frac{n}{2}$ [ 10 + (n - 1)3 ]

Then by comparison

2a₁ = 10 ( divide both sides by 2 )

a₁ = 4 ← initial value

and d = 3 ← common difference

Thus

$S_{8}$ = $\frac{8}{2}$ [ 10 + (7 × 3) ]

   = 4(10 + 21)

   = 4 × 31

   = 124