SOLUTION: √5/√3 + √(3)/√(5) + 3/5*√(3)/√(5)+... this is limitless sequence Sn is required

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Question 388736: √5/√3 + √(3)/√(5) + 3/5*√(3)/√(5)+... this is limitless sequence Sn is required
Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!
sqrt%285%29%2Fsqrt%283%29%22%22%2B%22%22sqrt%283%29%2Fsqrt%285%29%22%22%2B%22%22expr%283%2F5%29expr%28sqrt%283%29%2Fsqrt%285%29%29
%22%2B...%22
We check to see if it is a geometric series:

Dividing the second term by the first term:

sqrt%283%29%2Fsqrt%285%29%22%F7%22sqrt%285%29%2Fsqrt%283%29%22%22=%22%22sqrt%283%29%2Fsqrt%285%29%22%22%2A%22%22sqrt%283%29%2Fsqrt%285%29%22%22=%22%223%2F5

Dividing the third term by the second term:

expr%283%2F5%29expr%28sqrt%283%29%2Fsqrt%285%29%29%22%F7%22sqrt%283%29%2Fsqrt%285%29%22%22=%22%22expr%283%2F5%29expr%28sqrt%283%29%2Fsqrt%285%29%29%22%22%2A%22%22sqrt%285%29%2Fsqrt%283%29%22%22=%22%22expr%283%2F5%29expr%28cross%28sqrt%283%29%29%2Fcross%28sqrt%285%29%29%29%22%22%2A%22%22cross%28sqrt%285%29%29%2Fcross%28sqrt%283%29%29%22%22=%22%223%2F5

Since we got the same thing both times, it's a geometric series
and the common ratio is what we got, namely 3%2F5

The formula for the infinite sum is:

S%5Binfinity%5D%22%22=%22%22a%5B1%5D%2F%281-r%29

where a%5B1%5D=sqrt%285%29%2Fsqrt%283%29

Let's rationalize the denominator of that



and r=3%2F5. Substituting:

S%5Binfinity%5D%22%22=%22%22expr%28sqrt%2815%29%2F3%29%2F%281-3%2F5%29%22%22=%22%22expr%28sqrt%2815%29%2F3%29%2F%282%2F5%29%22%22=%22%22expr%28sqrt%2815%29%2F3%29%2Aexpr%285%2F2%29%22%22=%22%225sqrt%2815%29%2F6

Edwin