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juin [17]
3 years ago
15

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

Mathematics
1 answer:
mote1985 [20]3 years ago
8 0

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

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