IXL - Write variable expressions for arithmetic and geometric sequences (Algebra 1 practice)

Write
an
equation
to
describe
the
sequence
below.
Use
n
to
represent
the
position
of
a
term
in
the
sequence,
where
n = 1
for
the
first
term.

...

Write your answer using decimals and integers.

an = ()n - 1

ref_doc_title.

Learn with an example

question

Write an expression to describe the sequence below. Use n to represent the position of a term in the sequence, where n = 1 for the first term.

5, 10, 15, 20, ...

an =

solution

The sequence 5, 10, 15, 20, ... looks like 1, 2, 3, 4, ... except each term is 5 times as large. So, the expression that describes the sequence is 5n, where n represents the position of a term in the sequence. Check the first four terms:

To find the 1^st term, plug in n = 1.

5n = 5(1) = 5

To find the 2^nd term, plug in n = 2.

5n = 5(2) = 10

To find the 3^rd term, plug in n = 3.

5n = 5(3) = 15

To find the 4^th term, plug in n = 4.

5n = 5(4) = 20

The sequence 5, 10, 15, 20, ... is described by the expression 5n.

Looking for more? Try these:

Lesson: Geometric sequences

Lesson: Arithmetic sequences

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Not feeling ready yet? These can help:

U.7Write variable expressions for arithmetic sequences

U.8Write variable expressions for geometric sequences

Lesson: Geometric sequences

Lesson: Arithmetic sequences

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