Question

Find the sum of the arithmetic sequence. (1 point)

-10, -7, -4, -1, 2, 5, 8

Answer 1

@UnkleRhaukus

Answer 2

sum = (n/2) (a1 + l)

Answer 3

i don't get what that equations mean lol

Answer 4

where n = number of terms, a1 = first term and l = last term

Answer 5

here n = 7 , a1 = -10 and l = 8

Answer 6

just plug those values into the formula and work it out

Answer 7

= (7/2) * (-10+8)
= (7/2) * -2
= ?

Answer 8

or, in this short case, you can add them one by one, may be a little bit faster ;)

Answer 9

yes true - but its a good idea to remember the formula as well

Answer 10

okay i have another question

Answer 11

@welshfella

Answer 12

?

Answer 13

for geometric sequence there are two formulas to find sum
it depends on ratio
if ratio is less than then you have to apply infinite geometric formula \[\large\rm \left| r \right| <1 \]
\[\huge\rm s_n = \frac{ a_1 }{ 1-r }\]
and if ratio is greater than one then use finite geo. \[\huge\rm s_n = a_1 ( \frac{ 1 -r^n }{ 1-r })\]

Answer 14

its going smaller does that matter?

Answer 15

what is ratio ?? r= ??
do you know how to find ratio ?

Answer 16

no

Answer 17

to find ratio divide next term by one before term \[\huge\rm r = \frac{ a_2 }{ a_1 } , \frac{ a_4 }{ a_3 }\]

Answer 18

so is the answer 1/768?

Answer 19

@Nnesha

Answer 20

how did you get that ?

Answer 21

i added all of them

Answer 22

r is less than one ??

Answer 23

yes

Answer 24

so apply infinite geo. formula

Answer 25

so is my answer right?