Question

Find the sum of first n terms of the following A.P. *
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Answer 1

Answer:

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

Step-by-step explanation:

sum of first n terms = Sn

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

n = number of terms

a = first term of A.P.

d = common difference

Hope it helps

Answer 2

Answer:

sum of first n terms of an AP is  n(n+1)/2

Step-by-step explanation:

we have to find the sum of first n terms of AP

AP can be from 1,2,3,4,5,6,7,8,  up to n terms

because the perfect data for an AP is not given.

the formula for finding sum of n terms of the AP is

Sₙ = (n/2)(2a + (n-1)d)

where a = first term of AP

d = difference of AP

assume first term a = 1;

difference d = (2-1) = 1

substitute these values in Sₙ formula.

Sₙ = (n/2)(2 + (n-1))

= (n/2)(2 + n -1)

= (n/2)(n + 1)

= n(n+1)/2

sum of first n terms of an AP is  n(n+1)/2