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Summation by parts. In mathematics, summation by parts transforms the summation of products of sequences into other summations, often simplifying the computation or (especially) estimation of certain types of sums. It is also called Abel's lemma or Abel transformation, named after Niels Henrik Abel who introduced it in 1826.
For this sequence, Abel's summation formula simplifies to. Similarly, for the sequence and for all , the formula becomes. Upon taking the limit as , we find. assuming that both terms on the right-hand side exist and are finite. Abel's summation formula can be generalized to the case where is only assumed to be continuous if the integral is ...
Sums of partially ordered sets. Another way to combine two (disjoint) posets is the ordinal sum (or linear sum), Z = X ⊕ Y, defined on the union of the underlying sets X and Y by the order a ≤ Z b if and only if: a, b ∈ X with a ≤ X b, or; a, b ∈ Y with a ≤ Y b, or; a ∈ X and b ∈ Y. If two posets are well-ordered, then so is ...
The partial sums of the series 1 + 2 + 3 + 4 + 5 + 6 + ⋯ are 1, 3, 6, 10, 15, etc.The nth partial sum is given by a simple formula: = = (+). This equation was known ...
In algebra, the partial fraction decomposition or partial fraction expansion of a rational fraction (that is, a fraction such that the numerator and the denominator are both polynomials) is an operation that consists of expressing the fraction as a sum of a polynomial (possibly zero) and one or several fractions with a simpler denominator. [1]
Convergent series. In mathematics, a series is the sum of the terms of an infinite sequence of numbers. More precisely, an infinite sequence defines a series S that is denoted. The n th partial sum Sn is the sum of the first n terms of the sequence; that is, A series is convergent (or converges) if and only if the sequence of its partial sums ...
Running total. A running total or rolling total is the summation of a sequence of numbers which is updated each time a new number is added to the sequence, by adding the value of the new number to the previous running total. Another term for it is partial sum . The purposes of a running total are twofold. First, it allows the total to be stated ...
The basic idea is similar to Leibniz's probabilistic approach: essentially, the Cesàro sum of a series is the average of all of its partial sums. Formally one computes, for each n, the average σ n of the first n partial sums, and takes the limit of these Cesàro means as n goes to infinity. For Grandi's series, the sequence of arithmetic means is