IXL | Write variable expressions for arithmetic sequences

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.

^–4, ^–8, ^–12, ^–16, ...

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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.

2, 4, 6, 8, ...

solution

The sequence 2, 4, 6, 8, ... looks like 1, 2, 3, 4, ... except each term is 2 times as large. So, the expression that describes the sequence is 2n, 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.

2n = 2(1) = 2

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

2n = 2(2) = 4

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

2n = 2(3) = 6

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

2n = 2(4) = 8

The sequence 2, 4, 6, 8, ... is described by the expression 2n.

Looking for more? Try these:

Lesson: Arithmetic sequences

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Not feeling ready yet? These can help:

V.6Evaluate variable expressions for sequences

MM.10Write a two-variable equation

Lesson: Arithmetic sequences

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