IXL - Evaluate recursive formulas for sequences (Algebra 2 practice)

Find

and

a
1
=
–
7
a
n
=
a
n
–
1
+
12

Write your answers as integers or fractions in simplest form.

a
2
=
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c
c
a
3
=
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c

ref_doc_title.

Learn with an example

question

Find

and

a
1
=
2
a
n
=
2
a
n
–
1

Write your answers as integers or fractions in simplest form.

a
2
=
c
a
3
=
c

key idea

A sequence is an ordered list of numbers, called

terms.

The terms in a sequence are sometimes written

etc., where

is the first term,

is the second term, and so on. The subscript

on the term

is called the

index.

A recursive formula defines a sequence using earlier terms.

solution

Look at the recursive formula. (It is recursive because it defines

using the earlier term

–

Find

Plug

into the indices and use the value of

–

Plug in

(

)

Plug in

Find

Plug

into the indices and use the value of

–

Plug in

(

)

Plug in

The terms are:

a
2
=
4
a
3
=
8

Looking for more? Try these:

Lesson: Arithmetic sequences

Lesson: Geometric sequences

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Teacher tools

Work it out

Not feeling ready yet? These can help:

B.2Evaluate variable expressions involving integers

Lesson: Arithmetic sequences

Lesson: Geometric sequences

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