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Cat fac 1+2+3+4.......+99

Răspuns :

49+50=99 1+2+3+4+...+99 = (1+98)x49 + 99 = 4950 .
1+98 = 99 .
2+97 = 99 .
3+96 = 99 .
......
49+50=99 .
:)
1+2+3+4+.........+99=
n=(99 - 1) : (2-1 ) +1
n=98 : 1+1
n=99
S=[(99+1) 
×99] :2=
S=( 100 
×99) : 2 =
S=9900 :2
S=4950.