# Recursive equations to write a sequence

DO NOT multiply the 2 and the 3 together. Write recursive equations for the sequence 2, 4, 8, 16, Since our recursion involves two previous terms, we need to specify the value of the first two terms: Examples Find the recursive formula for 15, 12, 9, 6.

Look at the example below to see what happens. Notice that the an and n terms did not take on numeric values. We have r, but do not know a1. Now we have to simplify this expression to obtain our final answer. Your formulas should be simplified if possible, but be very careful when working with exponential expressions.

If you need to review these topics, click here. What does this mean? There can be a rd term or a th term, but not one in between. Find the recursive formula for 5, 10, 20, 40. Find a6, a9, and a12 for problem 8. Rather than write a recursive formula, we can write an explicit formula. Find a10, a35 and a82 for problem 4.

Given the sequence 2, 6, 18, 54. What is your answer? You will either be given this value or be given enough information to compute it. So 3 must be raised to the power as a separate operation from the multiplication.

Write recursive equations for the sequence 5, 7, 9, 11, Find the explicit formula for 0. To write the explicit or closed form of an arithmetic sequence, we use an is the nth term of the sequence.

In this lesson, it is assumed that you know what an arithmetic sequence is and can find a common difference. This sounds like a lot of work. To find the 50th term of any sequence, we would need to have an explicit formula for the sequence. The first term is 2, and each term after that is twice the previous term, so the equations are: However, the recursive formula can become difficult to work with if we want to find the 50th term.

We already found the explicit formula in the previous example to be. If neither of those are given in the problem, you must take the given information and find them.

Since we did not get a whole number value, then is not a term in the sequence. Notice this example required making use of the general formula twice to get what we need. The formula says that we need to know the first term and the common ratio.

What is your answer? Well, if is a term in the sequence, when we solve the equation, we will get a whole number value for n. Now we use the formula to get Notice that writing an explicit formula always requires knowing the first term and the common ratio. Find the explicit formula for 5, 10, 20, 40.

In a geometric sequence, each term is obtained by multiplying the previous term by a specific number. For example, when writing the general explicit formula, n is the variable and does not take on a value.

Site Navigation Arithmetic Sequences This lesson will work with arithmetic sequences, their recursive and explicit formulas and finding terms in a sequence. In this situation, we have the first term, but do not know the common difference.

The way to solve this problem is to find the explicit formula and then see if is a solution to that formula. If you need to review these topics, click here.

In this situation, we have the first term, but do not know the common ratio.Example fresh-air-purifiers.com recursive equations for the sequence f5;7;9;11;g.

Recursive sequences are sometimes called a difference equations. The recursive se-quence in Example 1 is called a ﬁrst-order difference equation because an depends on just the preceding term an1. In mathematics, a recurrence relation is an equation that recursively defines a sequence or multidimensional array of values, once one or more initial terms are given: each further term of the sequence or array is defined as a function of the preceding terms.

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.

Sep 23,  · How to write quadratic recursive equations. This feature is not available right now. Please try again later. Visualization of a Recursive sequence Pascal's Triangle is one of the most famous recursive sequences in mathematics.

Below is a visualization of how Pascal's Triangle works. As you can see each term in the triangle is. ©x 61M2X fK cu4t Paj QS3o 2fkt XwoaOrpe N YL1LzCt.

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Recursive equations to write a sequence
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