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Consider a function f : N → R, satisfying f

1. + 2f
2. + 3f
3. + .... + xf ( x ) = x ( x + 1 ) f ( x ) ; x  2 with f
4. =1. Then ) 2028 ( f 1 ) 2022 ( f 1  is equal to (1) 8200 (2) 8400 (3) 8100 (4) 8000

Correct answer: + .... + xf ( x ) = x ( x + 1 ) f ( x ) ; x  2 with f

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