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Concept

Index

Sometimes instead of using different variables for different values, an index is used with the same variable. To distinguish between values, the index is written as a subscript to the term.

Indices can be used to specify multiple solutions of an equation or unknown terms of a sequence. $a_1, \ a_2, \ a_3, \ldots, \, a_n$ Since there is a finite number of letters, writing these unknown terms in this way, rather than $a,$ $b,$ $c,\ldots,$ allows more flexibility in expressing the sequence.