Mathematics
Grade 11
15 min
Evaluate recursive formulas for sequences
Evaluate recursive formulas for sequences
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1
Introduction & Learning Objectives
Learning Objectives
Define a recursive formula and identify its components.
Calculate the first 'n' terms of a sequence given a recursive formula and an initial term.
Evaluate a specific term (e.g., the 6th term) of a sequence by applying the recursive rule iteratively.
Distinguish between a recursive formula and an explicit formula for a sequence.
Model simple real-world scenarios, like compound interest or population growth, using a recursive formula.
Use a calculator to accurately compute terms in sequences with more complex recursive rules.
Ever see a pattern in nature, like the spirals on a pinecone, and wonder how it's built? 🌲 Many of these patterns can be described by recursive formulas, where each step builds upon the last!
This tutorial will teach...
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Key Concepts & Vocabulary
TermDefinitionExample
SequenceAn ordered list of numbers, often following a specific pattern or rule. Each number in the list is called a term.The sequence of even positive integers is 2, 4, 6, 8, 10, ...
Recursive FormulaA formula that defines each term of a sequence by relating it to the preceding term(s). It consists of two parts: an initial term and a recursive rule.a_1 = 4 and a_n = a_{n-1} + 2. This means the first term is 4, and every subsequent term is 2 more than the one before it.
Initial Term(s)The first term (or first few terms) of a sequence, which is given explicitly. This is the starting point for the sequence.In the formula a_1 = 10 and a_n = 2 * a_{n-1}, the initial term is a_1 = 10.
Recursive RuleThe part of the formula that specifies how to calculate the nth term (a_n)...
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Core Formulas
General First-Order Recursive Formula
Given a_1, a_n = f(a_{n-1}) for n > 1
This is the standard form where the next term (a_n) is some function of the immediately preceding term (a_{n-1}). To find any term, you must know the term before it.
Recursive Formula for an Arithmetic Sequence
Given a_1, a_n = a_{n-1} + d for n > 1
Used for sequences where a constant difference, 'd', is added to each term to get the next. 'd' is the common difference.
Recursive Formula for a Geometric Sequence
Given a_1, a_n = a_{n-1} * r for n > 1
Used for sequences where each term is multiplied by a constant ratio, 'r', to get the next. 'r' is the common ratio.
General Second-Order Recursive Formula
Given a_1 and a_2, a_n = f(a_{n-1},...
5 more steps in this tutorial
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Sign Up Free to ContinueSample Practice Questions
Easy
What are the two essential components of a recursive formula for a sequence?
A.The first term and the last term
B.An initial term and a recursive rule
C.The common difference and the common ratio
D.An explicit formula and the term number 'n'
Easy
Given the recursive formula a_1 = 7 and a_n = a_{n-1} - 4, what is the value of the second term, a_2?
A.7
B.11
C.3
D.-4
Easy
A sequence is defined by a_1 = 5 and a_n = 3 * a_{n-1}. What kind of sequence is this?
A.An arithmetic sequence
B.geometric sequence
C.second-order sequence
D.constant sequence
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