Question 1048108
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Geom. progression,
first term 1,
the common difference -2.


{{{a[n+1]}}} = {{{(-2)*a[n]}}}, n = 1, 2, 3, . . . 


General term  {{{a[n]}}} = {{{1*(-2)^(n-1)}}} = {{{(-2)^(n-1)}}} = {{{(-1)^(n-1)*2^(n-1)}}}.
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