Question

If the sum of n terms of an A.P. be 3n² + n and its common difference is 6, then its first term is ______.

पर्याय

• 2

• 3

• 1

• 4

Answer 1

If the sum of n terms of an A.P. be 3n² + n and its common difference is 6, then its first term is 4.

Explanation:

In the given problem, the sum of n terms of an A.P. is given by the expression,

S_n = 3n² + n

Here, we can find the first term by substituting n = 1 as sum of first term of the A.P. will be the same as the first term. So we get,

S_n = 3n² + n

S₁ = 3 (1)² + (1)

= 3 + 1

= 4

Therefore, the first term of this A.P is a = 4.