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a fost răspuns

pe o dreapta se iau in ordine punctele:A1,A2,A3,....A200,astfel incat A1A2=4cm,A2A3=8CM,a3a4=12CM...
A)CE LUNGIME ARE [a1a200]?
B)ce lungime are [A100A200]?

Răspuns :

Miky93
a) a1a200= 4+8+12+....400= 4(1+2+3+...+100)= 4*(1+100)*100/2=

=200*101= 20200

b)a100a200= 400+404+408+....+800= 4(100+101+200)=4*(100+200)*100/2=

=200*300= 60000