Recursion is the process of choosing a starting term and repeatedly applying the same process to each term to arrive at the following term. Recursion requires that you know the value of the term immediately before the term you are trying to find.
Speaking about the Arithmetic Sequence Recursive Formula, it has two parts: first, a starting value that begins the sequence and a recursion equation that shows how terms of the sequence related to the preceding terms.
The recursive formula for an arithmetic sequence with common difference d is;
Arithmetic Sequence Recursive formula may list the first two or more terms as starting values depending upon the nature of the sequence. However, the an portion is also dependent upon the previous two or more terms in the sequence.
Examples Using the Formula for Arithmetic Sequence Recursive
Here are a few example questions:
Example 1:
Write the first four terms of the sequence when: a1= – 4 and an = an−1 + 5
Solution:
In recursive formulas, each term is used to produce the next term. Follow the movement of the terms through the steps given below.
Given:
a1= – 4
And
an = an−1 + 5 (each term is 5 more than the term before)
n = 2
a2= a2−1 + 5
a2 = -4 +5
a2 = 1
n = 3
a3 = a3−1 + 5
a3 = 1 + 5
a3 = 6
n = 4
a4 = a4−1 + 5
a4 = 6 + 5
a4 = 11
Answer: -4, 1, 6, 11
Example 2: Find the recursive formula when the sequence 2, 4, 6, 8, 10….
Solution:
Considering this sequence, it can be represented in more than one manner. The given sequence can be represented as either an explicit (general) formula or a recursive formula.
Explicit Formula: an = 2n
Recursive Formula: a1 = 2 and an = an−1 + 2
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So I have learned to program using recursion, but I have not learned how to actually do this in math. If I have the sequence {4,8,12}, and the question asks for a recursive formula to solve for an+1, would it be as simple as: an+1 = an + 4 ? This seems correct to me, but it also seems too simple.
asked Nov 16, 2016 at 23:36
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If the explicit formula for a sequence is $a_n=a_1+n(d-1)$, then the recursive formula is $a_n=a_{n-1}+d$. Here, we have that the explicit formula is $a_n=4+4(n-1)$, then the recursive formula will be $a_n=a_{n-1}+4$. You are correct.
answered Mar 25, 2020 at 18:58
4yl1n4yl1n
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We saw in Sequences - Basic Information, that sequences can be expressed in various forms. Certain sequences (not all) can be defined (expressed) in a "recursive" form. A recursive formula designates the starting term, a1, and the nth term of the sequence, an , as an expression containing the previous term (the term before it), an-1.
To summarize the process of writing a recursive formula for an arithmetic sequence:
To summarize the process of writing a recursive formula for a geometric sequence:
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