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What is the 20th term of the arithmetic sequence 2, –4, –10, … ?

1 Answer

Feb 8, 2016

After the first term you obviously subtract $6$ $6$ at every step.

Explanation:

At the 20th term you must have done this 19 times.
So the 20th term is $2 - (19 \cdot 6) = - 112$ $2-(19*6)=-112$

Watch it!
Most of the times the first term is called $t_{0}$ $t_0$ .
This means that the 20th term is then $t_{19}$ $t_19$

But if they ask you for $t_{20}$ $t_20$ (=21th) it's different:
$t_{20} = 2 - (20 \cdot 6) = - 118$ $t_20=2-(20*6)=-118$

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