Question

where to use a+(n-1)d and Sn = 2a + +(n-1)d in Arithmetic progression please explain clearly ​

Answer 1

Answer:

1.an+(n-1)d,2.sn=n/2(2a+(n-1)d)

Step-by-step explanation:

1.this formula is used for finding an,n'th term and sometimes to find a,d also

2.this is used for finding the sum of the term in an AP

Answer 2

U have written wrong formula of Sum

Right formula is below

Step-by-step explanation:

a + ( n - 1 ) d = term on n position

Example

4 , 10 , 16 , 22 are in AP

a = 4 , d = 6 4 th term = 22

n = 4

22 = 4 + ( 4 - 1 ) 6

To find Sum of an AP

Sum formula is used

Sum = n÷2 [2a + ( n - 1 ) d ]

1 , 3 , 5 , 7 are in AP

a = 1 , d = 2 , n = 4

Sum = 4÷2 [ 2 × 1 + ( 4 - 1 ) 2]

= 16