Identify the 12th term of a geometric sequence where a1 = 8 and a6 = -8,192. PLS HELP. Will fan and give medal. :)

Question

anonymous · Answer

A. 134,217,728	
	B. 33,554,432	
	C. -33,554,432	
	D. -134,217,728

campbell_st · Answer

well before you find the term, you need the common ratio r

a term in a geometric series is 

$$a_{n} = a_{1} \times r^{n - 1}$$

so use the 6th term, n = 6 and the 1st term to find r

$$-8192= 8 \times r^{6 - 1}~~~~~or~~~~~~~ -8192 = 8 \times r^5$$

solve for r

when you get it substitute back into the 1st formula with n = 12 and a1 = 8 to find the 12th term

hope it helps

anonymous · Answer

I got C for the answer.

campbell_st · Answer

C was my answer... well done

anonymous · Answer

Great, thank you so much for all your help!