Notes On Sum of n Terms - CBSE Class 10 Maths
             An A.P is a sequence of numbers or terms in which each term except the first one is obtained by adding a fixed number or constant to the term preceding term.  The first term is denoted with â€˜aâ€™ and the fixed number is called the common difference denoted by â€˜dâ€™. The common difference is the difference between two successive terms that is t2 â€“ t1 = t3 â€“ t2 = t4 â€“ t3 =â€¦. Sum of n terms of an AP The sum of first n terms of an AP with first term 'a' and common difference 'd' is given by Sn = $\frac{\text{n}}{\text{2}}$[ 2a + ( n - 1) d] or $\frac{\text{n}}{\text{2}}$[ a + l ] or $\frac{\text{n}}{\text{2}}$[ First term  + Last term]. where l = a + (n - 1) d is called the last term. If Sn be the sum of first n terms of sequence and tn be the nth term of sequence can be written as, nth term (tn) = Sn - Sn-1 and common difference(d) = an - an-1 = Sn - 2Sn-1 + Sn-2 .

#### Summary

             An A.P is a sequence of numbers or terms in which each term except the first one is obtained by adding a fixed number or constant to the term preceding term.  The first term is denoted with â€˜aâ€™ and the fixed number is called the common difference denoted by â€˜dâ€™. The common difference is the difference between two successive terms that is t2 â€“ t1 = t3 â€“ t2 = t4 â€“ t3 =â€¦. Sum of n terms of an AP The sum of first n terms of an AP with first term 'a' and common difference 'd' is given by Sn = $\frac{\text{n}}{\text{2}}$[ 2a + ( n - 1) d] or $\frac{\text{n}}{\text{2}}$[ a + l ] or $\frac{\text{n}}{\text{2}}$[ First term  + Last term]. where l = a + (n - 1) d is called the last term. If Sn be the sum of first n terms of sequence and tn be the nth term of sequence can be written as, nth term (tn) = Sn - Sn-1 and common difference(d) = an - an-1 = Sn - 2Sn-1 + Sn-2 .

Next
âž¤