Two cars start traveling in the same direction around a circular road that is 80 km long. The speed of one car is 92 km/h and th
2 answers:
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Answer:
S₁₅ = 645
Step-by-step explanation:
The sum to n terms of an arithmetic sequence is
=
[ 2a₁ + (n - 1)d ]
where a₁ is the first term and d the common difference
Using the nth term formula = 5n + 3 , then
a₁ = 5(1) + 3 = 5 + 3 = 8
a₂ = 5(2) + 3 = 10 + 3 = 13 , then
d = a₂ - a₁ = 13 - 8 = 5
Thus
S₁₅ = [ (2 × 8) + (14 × 5) ]
= 7.5( 16 + 70)
= 7.5 × 86
= 645
Assuming the series is
The series will converge if
We have
So the series will certainly converge if
, but we also need to check the endpoints of the interval.
If
, then the series is a scaled harmonic series, which we know diverges.
On the other hand, if
, by the alternating series test we can show that the series converges, since
and is strictly decreasing.
So, the interval of convergence for the series is
.
The series will converge if
We have
So the series will certainly converge if
If
On the other hand, if
and is strictly decreasing.
So, the interval of convergence for the series is