"Hard" problem?
⎩ ⎪ ⎨ ⎪ ⎧ a = − b n = 1 a − 2 b + 3 a − 4 b + . . . + 2 0 1 7 a − 2 0 1 8 b n = 1 a − 2 b + 3 a − 4 b + . . . + 2 0 1 7 a − 2 0 1 8 b
Enter your answer as the value of n ( a + b ) .
Note: You may use i to denote − 1 midway through your working although your final answer should not contain i .
The answer is 0.
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Once you realize that a + b = 0 because a = − b you do not need to think harder anymore.
Good one, Stephen! Almost got me!