Question

If the nth term of AP is (2n+1), find the sum of first n terms of the AP​

Answer 1

Answer:

an = 2n +1

Taking n= 1,2

a1 = 2×1 +1

= 2+1

= 3

a2 = 2×2+1

= 4+1

= 5

d = a2 - a1

= 5 - 3

= 2

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

= n/2 ( 2×3+(n-1)2)

= n/2 ( 6+2n-2)

= n/2 (4+2n)

= 2n+n sq.

Okay

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