document.write( "Question 1188018: Given that the first term and the common ratio of a geometric sequence are 3/8 and -2 respectively, and the sum of the first n terms is -8,191.875, find the sum of the (n+1) term to the (n+5) term. \n" ); document.write( "
Algebra.Com's Answer #819067 by greenestamps(13200)\"\" \"About 
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\n" ); document.write( "S(n) = a+ar+ar^2+...+ar^(n-1)

\n" ); document.write( "S(n) = a(1+r+r^2+...+r^(n-1)

\n" ); document.write( "\"S%28n%29+=+a%28%281-r%5En%29%2F%281-r%29%29\"

\n" ); document.write( "We are given a=3/8, r=-2, and S(n) = -8191.875. Plug the numbers into the formula to determine n.

\n" ); document.write( "
\n" ); document.write( "\"1-%28-2%29%5En+=+8%28-8191.875%29=-65535\"
\n" ); document.write( "\"-%28-2%29%5En+=+-65536+=+-2%5E16\"
\n" ); document.write( "\"n=16\"

\n" ); document.write( "We are to find the sum of the (n+1) term to the (n+5) term, or the sum of the 17th to 21st terms, which is S(21)-S(16).

\n" ); document.write( "\"S%2821%29+=+%281%2F8%29%28%281-%28-2%29%5E21%29%29+=+262144.125\"

\n" ); document.write( "And then

\n" ); document.write( "\"S%2821%29-S%2816%29+=+262144.125-%28-8191.875%29+=+270336\"

\n" ); document.write( "ANSWER: 270336

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