Asked by Ellie

-Write the arithmetic sequence 21,13,5,-3... in the standard form:
a_n=

-a_n=a_1+(n-1)d--so a_n=21+(n-1)-8

*a_n=-168-8n
why isnt this right?
Answered by Quidditch
You are close. You have an error:
Your step:
a_n = 21 + (n - 1) - 8
should be:
a_n = 21 + (n - 1) * (-8)
Answered by Ellie
oh yeah sorry i wrote that wrong i put -168-8n but it still said my answer was wrong
Answered by Quidditch
a_n = 21 + (n-1)*(-8)
Expand that using the distributive law.
The first term, 21, is not multiplied by -8. Only the terms in parenthesis are multiplied by -8.
Answered by Ellie
i figured out what i was doing thank you so much!
Answered by Quidditch
You're very welcome.
Answered by Edward
arithmetic sequence
b_n=(-2)^(n-1)
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