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University of South Carolina High School Math Contest/1993 Exam/Problem 4

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Problem

If (1 + i)^{100} is expanded and written in the form a + bi where a and b are real numbers, then a =

\mathrm{(A) \ } -2^{50} \qquad \mathrm{(B) \ } 20^{50}  - \frac{100!}{50!50!} \qquad \mathrm{(C) \ } \frac{100!}{(25!)^2 50!}...

Solution

Notice that (1+i)^{2}=2i. We then have (2i)^{50}=-2^{50}.


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