Find S20 of the series whose first terms are: 30, 22, 14, 6, ...
1 answer:
Answer:
- 920
Step-by-step explanation:
There is a common difference d between consecutive terms in the sequence, that is
d = 22- 30 = 14 - 22 = 6 - 14 = - 8
This indicates the sequence is arithmetic with sum to n terms given by
=
[ 2a₁ + (n - 1)d ]
where a₁ is the first term and d the common difference
Here a₁ = 30 and d = - 8 , thus
=
[ (2 × 30) + (19 × - 8) ]
= 10(60 - 152)
= 10 × - 92
= - 920
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<u><em>Hope this helps! Let me know if you have any questions</em></u>