Answer: Choice A, [tex]a_n = -5n+12[/tex]
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Explanation:
[tex]a_1 = 7[/tex] is the first term
[tex]d = -5[/tex] is the common difference, telling us to add -5 to each term to get the next term. This is the same as subtracting 5 from each term
The nth term of the arithmetic sequence is,
[tex]a_n = a_1 + d(n-1)\\\\a_n = 7 + (-5)(n-1)\\\\a_n = 7-5(n-1)\\\\a_n = 7-5n+5\\\\a_n = -5n+12\\\\[/tex]
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As a check, let's plug in n = 4 and we should get -8 as our fourth term
[tex]a_n = -5n+12\\\\a_4 = -5(4)+12\\\\a_4 = -20+12\\\\a_4 = -8\\\\[/tex]
so that confirms that portion of the sequence. I'll let you check the other values.
