Question

the sum of first n terms
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Answer 1

Step-by-step explanation:

The general form of an Arithmetic Progression is a, a + d, a + 2d, a + 3d and so on. Thus nth term of an AP series is Tn = a + (n - 1) d, where Tn = nth term and a = first term. Here d = common difference = Tn - Tn-1. The sum of n terms is also equal to the formula where l is the last term.

Answer 2

Step-by-step explanation:

If you are talking about Geometric Progression,

Sum of n terms can be calculated as follows:

$\frac{a( {r}^{n} - 1)}{r - 1}$

And, if you're talking of Arithmetic Progression, then Sum of n terms can be calculated as follows:

$\frac{n}{2} (a + (n - 1)d)$

where, n = number of terms, d = common difference, r = common ratio, a = first term of the sequence