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Calculati a) 1+2+3+4+.........+100 , b)2+4+6+.....+100, c)1+3+5+....+2013, d) (2+4+6......+4260 ) - (1+3+5+...+2013)

Răspuns :

Anny30834
a) (100×101):2=50×101=5050
b) 2(1+2+...+50)=2×(50×51):2= 50×51=2550
c)nr de termeni: (2013-1):2+1=1007
suma=[1007×(2013+1)]:2=1007×1007
d)2(1+2+...+2130)-1007×1007=
=2130×2131-1007×1007

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