This constant term is defined as common difference and it is denoted by ‘d’. Its first term is denoted by ‘a’, last term is denoted by an and determined by formula “a + (n - 1) d”. Sum of series is denoted by Sn and it is determined by the formula “n/2[2a + (n-1) d]”. To learn how to do sequences in Geometric Progression firstly we must know what geometric progression is. Geometric series is defined as the series in which Ratio of two consecutive terms is constant. Thus, it is defined as a series in which a constant term is multiplied to the terms of series to obtain the next term, this constant term which is multiplied to the terms is known as common ratio which is denoted by ‘r’, its first term is denoted by ‘a’, sum of series is denoted by Sn which is equals to Sn = a (1 – rn+1) / (1 - r) and its last term an is determined as arn-1.
Third type of series is defined as Harmonic series which is inverse of Arithmetic Series, it is same as Arithmetic Progression but the difference is that it is reciprocal of that arithmetic progression.