Question

The sum of an arithmetic sequence can be found by the formula Sn = n(2a

+ (n - 1)d). Use the formula to find the sum of first 10 terms of the sequence
{-3.2, 7, 12, 17. 22...)​

Answer 1

Explanation:

Hey there!

The given series: -3,2,7,12,17,22.....

Common ratio (d) = t2-t1

= 2+3

= 5

No of terms (n) = 10

First term (a) = -3

Now;

`sn = (n)/(2) (2a + (n - 1)d)`

Keeping all values we get;

`s10 = (10)/(2) (2 * - 3 + (10 - 1)5)`

Simplify it.

`s10 = 5( - 6 + 45)`

or, S10 = 195.

Therefore, S10 = 195.

Hope it helps!