Thread: calculating a limit

I need to calculate the limit of (1/3^(n+2)-1/5^(n+2))/(1/3^(n+1)-1/5^(n+1)) where n tends to infinity, i know the answer is 1/3 but I don't understand how you get that.
Can anyone explain? I will be grateful for any help.

Originally Posted by joesmith

I need to calculate the limit of (1/3^(n+2)-1/5^(n+2))/(1/3^(n+1)-1/5^(n+1)) where n tends to infinity, i know the answer is 1/3 but I don't understand how you get that.
Can anyone explain? I will be grateful for any help.

Consider




Now multiply top and bottom by and see what happens.

-Dan

Thanks i've just figured it out