Question

so i used the formula sn=n/2[2a+(n−1)d] but got -435 and that's not the right answer, someone help me find out what i did wrong?
Find S15 for the series -1 + -3 + -5 + -7 +…

Answer 1

can u find d??

Answer 2

Common difference

Answer 3

Can you show your work ??

Answer 4

d = t2 -t1

Answer 5

d=t2-t1

Answer 6

@waterineyes i think we should have went wrong in finding d

Answer 7

that is the only chance or calcu mistake

Answer 8

@Yahoo! let her give what she did..

Answer 9

Yup!

Answer 10

@summer1nthec1ty we can find your mistake can you show your work how you did it ??

Answer 11

[15/2(2(-1)+(15-1)*-4=-435

Answer 12

aha.......... d is wrong

Answer 13

d = t2 - t1

Answer 14

Difference is wrong I think...

Answer 15

Dang itt

Answer 16

-3 - (-1 ) = -2

Answer 17

\[\large d = -3 - (-1) = ??\]

Answer 18

-(-) = +

Answer 19

SHOOT thanks guys

Answer 20

welcome..))