Don't understand how they simplified this (ratio test)

  • #1
Don't understand how they simplified this....(ratio test)

I'm studying for my exam and I was looking at this example:

1.jpg




I'm not really sure how they get from here :

2.jpg


to here:

3.jpg



If someone could explain how they simplified this to me that would be fantastic...i'm really trying to understand series but sometimes the algebra stuff holds me up :-(.
 

Answers and Replies

  • #2
You are basically just dividing like terms, so you subtract exponents

(-3)^n+2 / (-3)^n+1 = (-3)^ ((n+2)-(n+1)) = -3

2^3n / 2^(3n+3) = 2^((3n) -(3n+3)) = 2^-3

hope that helps
 
  • #3
yes that helps...thank you :-)
 
  • #4
actually that helped a lot... thank you thank you!
 

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