Question

The sum of an arithmetic sequence can be found by the formula Sn=1/2 n(2a =(n-1)d). use the formula to find the sum of the first 10 terms of the sequence: -3,2.7,12,17,22,..

Answer 1

Answer:

Sn =195

Step-by-step explanation:

Sn = 1/2*n[2a+(n-1)d]

here n=10 (first 10 terms)

a= -3

d=5

therefore

Sn= 1/2* 10[ -6+(9*5)]

= 5[-6+45]

=5[39]

=5[40-1]

=200-5 = 195

Answer 2

Correct Question :

The sum of an arithmetic sequence can be found by the formula Sn=n/2(2a + (n-1)d). use the formula to find the sum of the first 10 terms of the sequence: –3,2,7,12,17,22,..

Answer:

The required sum of first 10 terms is 195

Step-by-step explanation:

In an Arithmetic Progression, sum of first n terms is given by,

$\boxed{\bf S_n = \dfrac{n}{2} [2a + (n-1)d]}$

where

n denotes the number of terms

a denotes the first term

d denotes the common difference

In the given A.P., –3 , 2 , 7 , 12 , 17 , 22 , ...

first term, a = –3

common difference is the difference between any two consecutive terms.

hence, d = 2 – (–3)

d = 2 + 3

d = 5

We have to find the sum of first 10 terms. So, put n = 10,

$\tt S_{10}=\dfrac{10}{2}[2(-3)+(10-1)(5) \\ \tt S_{10} = 5[-6+9(5)] \\ \tt S_{10}=5[-6+45] \\ \tt S_{10}=5(39) \\ \tt S_{10} = 195$

Therefore, the sum of first 10 terms of the given A.P is 195