What is the 7th term of the geometric sequence –1, 3, –9, …?

a. –2,187
c. 2,187
c. –729
d. 729

explain please so i no how...

Question

What is the 7th term of the geometric sequence –1, 3, –9, …?  

a. –2,187
c. 2,187
c. –729
d. 729

explain please so i no how...

auctoratrox · Answer

-729, you take the common ratio and keep multiplying until you get the desired result

parthkohli · Answer

$$\Large \color{purple}{\rightarrow -1(3^n) }$$

This is the formula. Now substitute n with 7.

anonymous · Answer

where did u get the formula? what is it?

parthkohli · Answer

I just saw the terms and then I made it.

auctoratrox · Answer

you find the common ratio (-3) and multiply it by itself until you get to the 7th term

anonymous · Answer

what about the -9 then? so is it a, or c?

auctoratrox · Answer

C, because to get to the next number of the geometric sequence, you must multiply the number before it by -3

auctoratrox · Answer

Parth your formula should be -1(3)^6

anonymous · Answer

I am not really understanding... :(

auctoratrox · Answer

okay, how do you get from -1 to 3 by multiplying?

anonymous · Answer

-3

auctoratrox · Answer

good! so your common ratio is r = -3. now, that that number and multiply it by the last number in the sequence, then tell me what you get.

anonymous · Answer

ok i get it i was like what was geometric sequence when i just it a few days ago...  sorry my mind went blank

auctoratrox · Answer

so -9 times -3 = 27, which is the fourth term. now find the seventh term.

parthkohli · Answer

Oh yes

anonymous · Answer

its c, -729, i just got it...

anonymous · Answer

thanks!