## trumpetmaster7777 2 years ago Given the sequence –3, 0, 3, which of the following is equivalent to:

1. trumpetmaster7777

$\sum_{n=5}^{8}A -subscript- N$

2. trumpetmaster7777

54 102 144 162

3. trumpetmaster7777

@primeralph @terenzreignz

4. trumpetmaster7777

@Zarkon

5. RolyPoly

First term is -3, common difference is 0-(-3) = 3 So, the sequence is $a_n = -3+3(n-1)$

6. trumpetmaster7777

so, we can do that plugging n-2, n-3 etc. into the next equations?

7. trumpetmaster7777

[-3+3(n-1)]+[-3+3(n-2)] etc.?

8. RolyPoly

You need to find sum from the fifth term to the eighth term, so, find a5, a6, a7, a8 and add them together.

9. RolyPoly

n is the number of term

10. trumpetmaster7777

that's right we start on 5 right? so like this?

11. RolyPoly

e.g. $a_5 = -3+3(5-1)=...$

12. RolyPoly

Start from 5, yes.

13. trumpetmaster7777

[-3+3(n-5)]+[-3+3(n-6)]+[-3+3(n-7)]+[-3+3(n-8)]?

14. trumpetmaster7777

(-3+3n-15)+(-3+3n-18)+ (-3+3n-21)+ (-3+3n-24)?

15. trumpetmaster7777

am I doing this right?

16. trumpetmaster7777

(3n-18)+(3n-21)+(3n-24)+(3n-x)+(3n-27)

17. trumpetmaster7777

i'm not sure what to do from there

18. RolyPoly

No

19. RolyPoly

$a_5 = -3+3(5-1)$$a_6 = -3+3(6-1)$$a_7 = -3+3(7-1)$... Then, find $$a_5+a_6+a_7+a_8$$

20. trumpetmaster7777

=−3+3(5−1) =−3+3(6−1) =−3+3(7−1) =-3+3(8-1)

21. trumpetmaster7777

=-6+15 =-6+18 =-6+21 =-6+24 =9 =12 =15 =18 9+12+15+18

22. trumpetmaster7777

54

23. trumpetmaster7777

thank you so much guys