Question

if nth term of an A. P is (2n+1),what is the sum of its first three terms ​

Answer 1

Answer:

n=3 an = (2n+1)

an =a+(n-1)d

2n+1=a+(3-1)d

2n+1= a+2d

Answer 2

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Given ,

nth term of AP = 2n + 1

So ,

First term = 2(1) + 1 = 3

Second term = 2(2) + 1 = 5

Third term = 2(3) + 1 = 7

Sum of first three term is 3 + 5 + 7 i.e 15

Hence , the sum of first three terms of an AP is 15