Page 100 - Numbertheory

@ @@Hßìÿaö§aI@†a‡Èÿa@óî‹Åä@ ()
()
. ()
. ()
. ()
. .

1, 2, 3, ... ,n ()
1+ 2 + 3 + ... + n = n (n +1)

2

( ) S = 1+ 2 + 3 + ... + (n −1) + n

S

( ) S = n + (n −1) + ... + 2 +1
() ()

2S = (1+ n ) + (2 + n −1) + (3 + n − 2) + ... + (n −1+ 2) + (n +1)
2S = (n +1) + (n +1) + (n +1) + ... + (n +1) + (n +1)
2S = n(n +1)

. S = n (n +1)

2

. n ()

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