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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*x = x.
2-nd term: i=3: = = = .
3-rd term: i=4: = = = .
4-th term: i=5: = = = .
Finally, the sum of these four terms is .
