Which of the following is the formula for the geometric sequence?

320, 80, 20, 5,...

an = 4(320)n-1

an = 320(4)n-1

an = 320(1/4)n-1

Question

Which of the following is the formula for the geometric sequence?

320, 80, 20, 5,...
 	
	
an = 4(320)n-1
	
an = 320(4)n-1
	
an = 320(1/4)n-1

anonymous · Answer

The last equation. The number before the ratio is the first term which dumbs the answers down to the last two. n is the position of a term. Try the position of one of them in the last two equations and see which one works. Or, you could just find the rate which is multiplying by 1/4. There is one answer for that.

solomonzelman · Answer

what common ratio between the terms do you see here?

solomonzelman · Answer

Or, do you notice any pattern in this sequence of numbers?