Question

find a_18 when a_1=27, d=-6

Answer 1

Using an arithmetic sequence that follows the formula: \(a_n =a_1 +(n-1)d\)

Answer 2

-75 is my answer

Answer 3

\[\large a_{\color{red}{n}} = a_{\color{red}{18}}\] Therefore we can conclude \(n=18\).

Let's see..

Answer 4

That is correct :)

Answer 5

thank you, but i did it the long way, d=-6
a_1=27
a_n=?

Answer 6

Perhaps you can show me how you've solved it?

Answer 7

i did 27-6=21
21-6=15
15-6=9 and so on until i got to a18.

Answer 8

but what is a_n?

Answer 9

That's also a good way to go about finding it.

Answer 10

it cant be 27(18-1)-6.

Answer 11

And why do you think it cant be?

Answer 12

because i got 453

Answer 13

and -2754 if i do the negative sign, first answer (453) i did a minus sign

Answer 14

This is how I solved it.\[a_n = a_{18} \longrightarrow n=18\]\[a_n=27+(18-1)(-6)\]\[a_n=27 -102\]\[a_n=-75\]

Answer 15

thats why, i forgot the addition sign.

Answer 16

:)

Answer 17

thank you ma'am!

Answer 18

No problem and good luck!