Question

Find the 32nd term of the sequence:
9, 4, -1, -6....

Answer 1

Just keep adding -5

Answer 2

so would it be -200 ?

Answer 3

a = 9, d = -5
32nd term = 9 +31(-5) =

Answer 4

how did you get -200?

Answer 5

Educate_me, there is a difference of -5 between every term and the next. There are 31 such steps between the first term and the 32nd. Therefore the 32nd term is 9 - 31(5) = -146

Answer 6

im confused.

Answer 7

what don't you understand? Let's try an example:
The 4th term of the sequence = a + (n-1)d
= a + (4-1)d
= a + 3d
= 9 + 3(-5)
= 9 - 15
= -6

Answer 8

I'm getting a different answer. You are trying to find the nth term or the 32nd term. So the difference is always -5. So your thingy will be -5n + (some number). Remember that number doesn't always work in the first and second case as is here.

Answer 9

After I did it again I got -146 ,

Answer 10

Yeah, Luminaire is right, I meant I got a different answer from Educateme. My method is -5n+14

Answer 11

Thaks guys... but one more question.. Write a recursive and an explicit formula for each sequence. 0, 6, 12, 18, 24 and 27, 15, 3, -9, -21

Answer 12

Do as I said earlier (remember in some cases it doesn't work in the first one or two cases). In the first one the difference is always 6. Therefore 6n + (some number). In each case you test, for the first case is 6 (1) + some number. What number added to 6 gives the next number and on.

Answer 13

but , how could we form a formula. the first sequence the common difference is 6and the first term is 0 ? so woud the formula be an=a1 (n-1) (6) ?

Answer 14

It doesn't say if you starting from 0 or 1. Let's assume you're starting at 1. It is 6n + 6. Or 6(1) + 6 which is 12, but remember, it doesn't always work in the first one or two terms. Just continue like that.

Answer 15

hmmm.

Answer 16

Actually, it should have been obvious to me the first one you gave starts at the zeroth term and works perfectly throughout 6n+6. See if you can do the second one.