# Write a recursive rule for the sequence

Recursive equations usually come in pairs: Recursion is the process of starting with an element and performing a specific process to obtain the next term. Write recursive equations for the sequence 2, 4, 8, 16, The recursive formula for an arithmetic sequence is written in the form For our particular sequence, since the common difference d is 4, we would write So once you know the common difference in an arithmetic sequence you can write the recursive form for that sequence.

You must substitute a value for d into the formula.

What is your answer? The explicit formula is also sometimes called the closed form. In this lesson, it is assumed that you know what an arithmetic sequence is and can find a common difference. Look at the example below to see what happens.

Find the explicit formula for 15, 12, 9, 6. Site Navigation Arithmetic Sequences This lesson will work with arithmetic sequences, their recursive and explicit formulas and finding terms in a sequence.

The way to solve this problem is to find the explicit formula and then see if is a solution to that formula.

This is enough information to write the explicit formula. However, the recursive formula can become difficult to work with if we want to find the 50th term. We have d, but do not know a1. Well, if is a term in the sequence, when we solve the equation, we will get a whole number value for n.

Find the recursive formula for 5, 9, 13, 17, 21. We already found the explicit formula in the previous example to be. If you need to review these topics, click here. The first term is 2, and each term after that is twice the previous term, so the equations are: So the explicit or closed formula for the arithmetic sequence is.

Write recursive equations for the sequence 2, 3, 6, 18,However, we have enough information to find it. Find the explicit formula for 5, 9, 13, 17, 21. Examples Find the recursive formula for 15, 12, 9, 6. To find the explicit formula, you will need to be given or use computations to find out the first term and use that value in the formula.

In an arithmetic sequence, each term is obtained by adding a specific number to the previous term. You must also simplify your formula as much as possible.

To write the explicit or closed form of an arithmetic sequence, we use an is the nth term of the sequence. Write recursive equations for the sequence 5, 7, 9, 11, This will give us Notice how much easier it is to work with the explicit formula than with the recursive formula to find a particular term in a sequence.

The first time we used the formula, we were working backwards from an answer and the second time we were working forward to come up with the explicit formula.

In this situation, we have the first term, but do not know the common difference. To find the 50th term of any sequence, we would need to have an explicit formula for the sequence.If a sequence is recursive, we can write recursive equations for the sequence.

Recursive equations usually come in pairs: the first equation tells us what the first term is, and the second equation tells us how to get the n th term in. Find the recursive formula of an arithmetic sequence given the first few terms. If you're seeing this message, it means we're having trouble loading external resources on our website.

Practice: Recursive formulas for arithmetic sequences.

Explicit formulas for arithmetic sequences. Explicit formulas for arithmetic sequences. Given the sequence: a) Write an explicit formula for this sequence.

b) Write a recursive formula for this sequence.

And, in the beginning of each lower row, you should notice that a new sequence is starting: first 0; then 1, 0; then –1, 1, 0; then 2, –1, 1, 0; and so on.

This is characteristic of "add the previous terms" recursive sequences. So once you know the common difference in an arithmetic sequence you can write the recursive form for that sequence.

However, the recursive formula can become difficult to work with if we want to find the 50 th term.

Learn how to find recursive formulas for arithmetic sequences. For example, find the recursive formula of 3, 5, 7.

Write a recursive rule for the sequence
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