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
You might be interested in
Answer:
8 years approximately
The problem (I'm assuming is):
Solve .
I put a t in the problem where I suspected it in went.
Step-by-step explanation:
Divide both sides by 100:
Rewrite in logarithm form.
Divide both sides by 0.05:
Put left hand side into calculator:
So about 8 years if I wrote down the equation correctly.