Using the nth term

Objective. Test whether a number is in a sequence.

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2. Worked example
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Learn: the key idea

Set the nth term expression equal to the number and solve. If n is a positive whole number, the value is in the sequence.

Worked example

Is 47 in the sequence 3n + 2?

1 $3n + 2 = 47.$
2 $3n = 45.$
3 $n = 15, a whole number.$

Answer: Yes, it is the 15th term

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Common mistake. Accepting a decimal or negative value of n as a valid position.

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