Question 613268
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Hi, 
Find the sum of the first four terms of the geometric sequence that starts with 3 and has r = 8.
  {{{sum( a[n], n=1, 4 ) = a[1]((1-8^4)/(1-8))}}} = 3(-4095/-7) = 1755

Find the sum of the following infinite geometric series, if it exists.
4 + 3 + 2.25 + 1.6875 +…
{{{sum( 4(3/4)^(n-1), i=1, infinity )}}} = {{{a[1]/(1-r)}}} = {{{4/(1/4)}}} = 16