Consecutive is remember-able (Part 8)
Evaluate:
Details:
The addition and subtraction are in a consecutive order of numbers:
The answer is -729.
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1 − 2 + 3 − 4 + 5 − … − 1 4 5 6 + 1 4 5 7 − 1 4 5 8
= ( 1 − 2 ) + ( 3 − 4 ) + ( 5 − . . . − 1 4 5 6 ) + ( 1 4 5 7 − 1 4 5 8 )
= − 1 − 1 − 1 − … − 1 − 1
= − ( 1 + 1 + 1 + … + 1 + 1 )
= − ( n = 1 ∑ 1 0 0 0 ( − 1 ) n + 1 n ) = − 7 2 9