Find an explicit formula for the arithmetic sequence 12, 5, -2, -9,... a(n)=

1 answer:

3 0

a is the beggining number and n is the amount of times needed to do this. if is 17 you would need to subtract 7 from the originol number 12 (a) that many times.

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Cynthia ran 4 laps in 40 minutes. Which ratio represents the number of laps ran to minutes?

poizon [28]

4:40 simplifies into 1:10

4 0

3 years ago

Find the 10th partial sum of the arithmetic sequence defined by

Evgesh-ka [11]

Answer:

22.5

Step-by-step explanation:

If you expand the series, you can see the first few terms of the series:

Putting 1 in $n$ , $\frac{1}{2}(1)-\frac{1}{2}=0$
Putting 2 in $n$ , $\frac{1}{2}(2)-\frac{1}{2}=0.5$
Putting 3 in $n$ , $\frac{1}{2}(3)-\frac{1}{2}=1$
Putting 4 in $n$ , $\frac{1}{2}(4)-\frac{1}{2}=1.5$

We can see the series is 0, 0.5, 1, 1.5, ....

This is an arithmetic series with common difference (the difference in 2 terms) 0.5 and first term 0.

We know formula for sum of arithmetic series:

$s_{n}=\frac{n}{2}(2a+(n-1)d)$

Where,

$S_{n}$ denotes the nth partial sum
$a$ is the first term (in our case it is 0)
$n$ is the term (in our case it is 10 since we want to find 10th partial sum -- sum until first 10 terms)
$d$ is the common difference (difference in term and the previous term) (in our case it is 0.5)