Question

@kirbykirby

Answer 1

Find the three arithmetic means in this sequence.

2, __, __, __, -18

Answer 2

average of 2 and -18 gives you the middle value

Answer 3

And I would find that by..what? Finding the mean?

Answer 4

Yes

Answer 5

\(2 + -18 = -16\)
\(-16 / 2 = -8\)

Answer 6

We subtract them and divide by four to find the common difference d. The intermediate means tells us there are four increments, thus we divide by four...so
-18-2=-20


-20 / 4 = -5
Thus d = -5 and our missing means are
2, -3, -8, -13, -18

Answer 7

Oh..

So now we have: 2, __, -8, __, -18

Answer 8

yes!

Answer 9

I don't follow..@cutepochacco

Answer 10

find the mean again for 2 and -8 to get the middle value

Answer 11

\(2 - 8 = -6\)
\(-6 / 2 = -3\)

Answer 12

I took -18 subtract 2=-20 then divide by 4

Answer 13

And do it again with -8 and -18, correct?

Answer 14

which comes out to -5
then to find the sequence take 2-5=-3
-3-5=-8
-8-5=-13
-13-5=-18

Answer 15

Exactly !

Answer 16

\(-8 - 18 = -26\)
\(-26 / 2 = -13\)

Answer 17

Awesome! Thanks!

That was a lot easier than I thought..

Answer 18

wait a sec, @cutepochacco 's method is more straightforward and it directly refers to arithmetic sequence instead of means.

Answer 19

its a good idea to know both the methods...