Question

-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?

Answer 1

You are close. You have an error:
Your step:
a_n = 21 + (n - 1) - 8
should be:
a_n = 21 + (n - 1) * (-8)

Answer 2

oh yeah sorry i wrote that wrong i put -168-8n but it still said my answer was wrong

Answer 3

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.

Answer 4

i figured out what i was doing thank you so much!

Answer 5

You're very welcome.

Answer 6

arithmetic sequence
b_n=(-2)^(n-1)