If the nth term of an A.P. is 2n + 1, then the sum of first n terms of the A.P. is
A. n (n – 2)
B. n (n + 2)
C. n (n + 1)
D. n (n –1)
Answers
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B. n (n + 2)
Step-by-step explanation:
nth term of an A.P. is 2n + 1
an = 2n+1
a = 2+1 = 3
a2 = 2(2) +1 = 5
a3 = 2(3) +1 = 7
So the AP is 3, 5, 7....
d = 5-3 = 2
Sum of n terms = n/2 (2a + (n-1)d)
= n/2 (2*3 +(n-1)2)
= n/2 (6 +2n -2)
= n/2 (4 +2n)
= n(n+2)
Option B is the answer.
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