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Calculati:
a) 1+3+5+.....+2003


Răspuns :

((1+2003)x2003):2=(2004x2003):2=4014012:2=2007006
a) 1+3+5+.....+2003 = (2003+1)*1002/2=1004*1002/2=503004

a₁=2n-1=2*1-1
a₂₀₀₃ =2*x-1
2003=2*x-1
2x=2004
x=1002