Question

If the nth term of an

a.P. Is 2n + 1, then the sum of first n terms of the

a.P. Is

Answer 1

Answer:

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Answer 2

Answer:

Step-by-step explanation:

here 2n+1 is nth term of AP,

to find out the AP, consider n as 1,2,3

So 2*1+1=3,2*2+1=5,2*3+1=7,

now a=3, d=2 ( since 7-5 and 5-3 both are equal to 2)

to find the nth term

S= n/2[a+l]

S= n/2[3+2n+1]

S= n/2[4+2n]

S=n[2+n]

Therefore S = n2+2n