Question

Write the sum of first n terms of the ap 2,9,16

Answer 1

Step-by-step explanation:

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

here d=a2-a1=9-2=7

Sn=n/2[(2×2)+(n-1)7]=n/2[4-7+7n] =n/2[7n-3]

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