The formula $$a_n = a_1 + (n - 1)d$$ can be used to give a formula for the general term of the arithmetic sequence. For example, the sequence $$3, 15, 27, 39, 51,\dots$$ has $$a_1 = 3$$ and common difference $$d = 12$$, hence a formula for the general term is given by $$a_n = 3 + (n - 1)\cdotp 12$$ which simplifies: $$a_n = 12n - 9$$. Now your turn: Which of the following is the general term $$b_n$$ of the sequence $$20, 18, 16, 14, 12, \dots$$?

Question

The formula $$a_n = a_1 + (n - 1)d$$ can be used to give a formula for the general term of the arithmetic sequence. For example, the sequence $$3, 15, 27, 39, 51,\dots$$ has $$a_1 = 3$$ and common difference $$d = 12$$, hence a formula for the general term is given by $$a_n = 3 + (n - 1)\cdotp  12$$ which simplifies: $$a_n = 12n - 9$$. Now your turn: Which of the following is the general term $$b_n$$ of the sequence $$20, 18, 16, 14, 12, \dots$$?

Uniteasy Admin · Accepted Answer

The common difference of the sequence $$20, 18, 16, 14, 12, \dots$$ is $$-2$$ and $$a_1=20$$.
Plug in the formula for the general terms of an arithmetic sequence, so we get,
$$a_n = a_1 + (n - 1)d=20+(n-1)(-2)=22-2n$$

Multiple Choice Question (MCQ)

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