How to write a recursive formula for a sequence

However, the recursive formula can become difficult to work with if we want to find the 50th term. Find the recursive formula for 0.

If we do not already have an explicit form, we must find it first before finding any term in a sequence. This is enough information to write the explicit formula. Look at the example below to see what happens. When writing the general expression for an arithmetic sequence, you will not actually find a value for this.

Find the explicit formula for 0. 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.

If you need to review these topics, click here. To find the 10th term of any sequence, we would need to have an explicit formula for the sequence.

Notice this example required making use of the general formula twice to get what we need. Find a6, a9, and a12 for problem 8.

If we simplify that equation, we can find a1. Find a6, a9, and a12 for problem 4. To write the explicit or closed form of an arithmetic sequence, we use an is the nth term of the sequence. This sounds like a lot of work.

Given the sequence 2, 6, 18, 54. If neither of those are given in the problem, you must take the given information and find them.

Write the explicit formula for the sequence that we were working with earlier.

Order of operations tells us that exponents are done before multiplication. However, we do know two consecutive terms which means we can find the common difference by subtracting. Find the explicit formula for 15, 12, 9, 6. Look at it this way.

But if you want to find the 12th term, then n does take on a value and it would be The recursive formula for a geometric sequence is written in the form For our particular sequence, since the common ratio (r) is 3, we would write So once you know the common ratio in a geometric sequence you can write the recursive form for that sequence.

a) Write an explicit formula for this sequence. b) Write a recursive formula for this sequence.

Learn how to find recursive formulas for arithmetic sequences. For example, find the recursive formula of 3, 5, 7, If you're seeing this message, it means we're having. 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. Using the recursive formula, we would have to know the first 49 terms in order to find the 50 th.

This sounds like a lot of work. There. The sequence of second differences is constant and so the sequence of first differences is an arithmetic progression, for which there is a simple formula.

A recursive equation for the original quadratic sequence is then easy. 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.

Download
How to write a recursive formula for a sequence
Rated 5/5 based on 51 review