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replace x,y from 2017 numbers with x+7xy+y, last (HOMC 2017 S Q5)

Source:

September 9, 2019
algebraFractioncombinatorics

Problem Statement

Write 20172017 following numbers on the blackboard: 10081008,10071008,...,11008,0,11008,21008,...,10071008,10081008-\frac{1008}{1008}, -\frac{1007}{1008}, ..., -\frac{1}{1008}, 0,\frac{1}{1008},\frac{2}{1008}, ... ,\frac{1007}{1008},\frac{1008}{1008} . One processes some steps as: erase two arbitrary numbers x,yx, y on the blackboard and then write on it the number x+7xy+yx + 7xy + y. After 20162016 steps, there is only one number. The last one on the blackboard is
(A): 11008-\frac{1}{1008} (B): 00 (C): 11008\frac{1}{1008} (D): 1441008-\frac{144}{1008} (E): None of the above