Question

sigma problem?

Answer 1

i got -42 but its not in the answer list :(

Answer 2

-24?

Answer 3

howd you get that? o.O

Answer 4

sum = -2(4)+5+-2(5)+5+-2(6)+5+-2(7)+5 = -24

Answer 5

Just sub. n = 4 , n=5, n=6, n=7 to the give general term and then add them all

Answer 6

ohhhh okay!! thanks!

Answer 7

yw

Answer 8

ALSO
\[\sum_{4}^{7}-2n+5\]
=\[-2\sum_{4}^{7}n+\sum_{4}^{7}5\]
=-2(4+5+6+7)+(5*4)
=-42+20=-24