Question

Find the 7th term of the geometric sequence –5, 15, –45, 135, –405,... a. –3,650
b. –3,645
c. 10,935
d. 1,215

Answer 1

a*r^1=15 I think
a*r^6=7th term

I think a is -5 use that to find it.

Answer 2

what about r ? i dont get it. im sorry im too stupid... @timo86m

Answer 3

U R not

the first term is always a so it is -5 in your case

the formula is
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ar^0=1st term , ar^1=2nd term and so on
_______________________________
Knowing that 2nd term is 15 and a is -5 we do this

-5*r=15 Using algebra we find that
r=-3

now we use the formula for the 7th term

ar^6

-5*(-3)^6=?

Answer 4

11390625? @timo86m

Answer 5

nooo :P

Answer 6

−3645 @timo86m

Answer 7

-5*(-3)^6=?
Lets leave the -5 outside for now shall we

-3*-3*-3*-3*-3*-3=729

now lets drop the -5 in
-5*(729) what is that :)

Answer 8

ooh pretty sure it will be negative 3645

Answer 9

−3645 !!!!!!!!!!!!!!!!!!!!!!!!!

Answer 10

@timo86m

Answer 11

oh sorry here all i see is

??? 3645

:)

but anyhoo i am pretty sure
-3645

Answer 12

yes i typed negative but it didnt show
thank you so much @timo86m

Answer 13

that is odd now i think i see them where as before they where ???

Answer 14

they looked like