What is the 7th term of the geometric sequence where a1 = -625 and a2 = 125? (1 points)

-0.2

0.04

-0.04

0.2

Question

What is the 7th term of the geometric sequence where a1 = -625 and a2 = 125? (1 points)
		
-0.2
		
0.04
		
-0.04
		
0.2

campbell_st · Answer

well start by finding the common ratio.... r

it can be found by using 

$$r = \frac{a_{2}}{a_{1}}$$

rishavraj · Answer

find the common ratio first of all...nd then find the seventh term

anonymous · Answer

Ok So Its Going To Be r= 125/-625 @campbell_st

campbell_st · Answer

well you can simplify that fraction...

then use the formula you have been given 2 or 3 times before for the sum of a geometric series

anonymous · Answer

I Got 0.2

campbell_st · Answer

ok... oops so a term in a series is 

$$a_{n} = a_{1} \times r^{n - 1}$$

you know the 1st term, common ratio r  and n = 7

substitute and then calculate

campbell_st · Answer

and you value of r should be r = -0.2

anonymous · Answer

oh ok

anonymous · Answer

so its going to be $$-625\times \left( -0.2 \right)^n-1$$ But wat is n

anonymous · Answer

@campbell_st