Question

Find an equation for the nth term of the arithmetic sequence.

a14 = -33, a15 = 9

Answer 1

what makes a sequence arithmetic?

Answer 2

t14=a+13d ................i
t15=a+14d.................ii
solve these two equations first (simultaneous equations)

Answer 3

How do I do that?

Answer 4

look,
i'm solving it .observe it carefully,ok

Answer 5

this is really simpler than solving a system of equation ...

what makes a sequence arithmetic?

Answer 6

I'm not really sure

Answer 7

they have a common difference>?

Answer 8

yes; a sequence is arithmetic of you can add the same value each time to get to the next number

Answer 9

so, to get from the 14th to the 15th values, we added what?

-33+d=9

Answer 10

d=42?

Answer 11

t14=a+13d ................i
t15=a+14d.................ii
so, now
a+13d=-33......i
a+14d=9..........ii
now subtracting i from ii;
-d=-42
d=42
now put d in equation ii;
a+14*42=9
a=579
now tn=579+(n-1)42
=579+42n-42
=537+42n

Answer 12

good

then we have some setup such that: an = a1 + 42(n-1)

using either of the given values we can easily determine a1

Answer 13

a15 = a1 + 42(15-1)

9 = a1 + 42(14)

9 - 42(14)= a1

Answer 14

a1 only has one value

Answer 15

a1=-579?

Answer 16

correct, so out equation is:

an = -579 +42(n-1)

Answer 17

yes lol i'm so sorry .yes a1=-579

Answer 18

Awesome! thank you guys a lot!!

Answer 19

good luck

Answer 20

would u mind helping me with another?

Answer 21

so answer will be -621+42n

Answer 22

ur welcome.no not at all

Answer 23

that result is suitable as well

Answer 24

I'll post it and tag you guys

Answer 25

thanx ami and jquelly for helping and correcting me

Answer 26

ok