find the sum of n terms if nth term is (2n+1)
Answers
Answered by
4
Nth term = 2×n + 1
First term = a = 2×1+1 = 3
2nd term = 2×2+1= 5.
Common difference = d = 5-3= 2.
Sum of first n terms = Sn = n/2 * [2a + (n-1) d]
Sn = n/2 × [6+(n-1)2] = n^2 + 2n.
======
We can also find the sum of first n terms by using the Sigma or summation of n & 1.
Sn = 2 × Sigma n + Sigma 1
= 2 × n(n+1)/2 + n
= n^2 + n + n
= n^2 + 2n
First term = a = 2×1+1 = 3
2nd term = 2×2+1= 5.
Common difference = d = 5-3= 2.
Sum of first n terms = Sn = n/2 * [2a + (n-1) d]
Sn = n/2 × [6+(n-1)2] = n^2 + 2n.
======
We can also find the sum of first n terms by using the Sigma or summation of n & 1.
Sn = 2 × Sigma n + Sigma 1
= 2 × n(n+1)/2 + n
= n^2 + n + n
= n^2 + 2n
kvnmurty:
:-)
this is an arithmetic progression AP
Nice answer sir
Similar questions