Question 1049687
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Expand the following sums:

c) the summation from 2 to 5 of (-1)^i(x^(i-1))
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1-st term:  i=2:   {{{(-1)^i*x^(i-1)}}} = {{{(-1)^2*x^(2-1)}}} = 1*x = x.


2-nd term:  i=3:   {{{(-1)^i*x^(i-1)}}} = {{{(-1)^3*x^(3-1)}}} = {{{-1*x^2}}} = {{{-x^2}}}.


3-rd term:  i=4:   {{{(-1)^i*x^(i-1)}}} = {{{(-1)^4*x^(4-1)}}} = {{{1*x^3}}} = {{{x^3}}}.


4-th term:  i=5:   {{{(-1)^i*x^(i-1)}}} = {{{(-1)^5*x^(5-1)}}} = {{{-1*x^4}}} = {{{-x^4}}}.


Finally, the sum of these four terms is  {{{x - x^2 + x^3 - x^4}}}.
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