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a fost răspuns

stabiliti parietatea numerelor; s1=2+4+6+...+198 s2=1+3+5+...175 s3=5+9+13+...+101 s4=5+10+15+...+85

Răspuns :

Robytzzu
S1=2•1+2•2+2•3+...+2•99=2•(1+2+3+...+99)=2•(99•100):2= 2•9900:2=19800:2=9900 ; S2=(175+1)•[(175-1):3+1]:2=176•(174:3+1):2=176•59:2=10384:2=5192; S3=(101+5)•[(101-5):3+1]:2=106•(96:3+1):2=106•33:2=3498:2=1749; S4=5•1+5•2+5•3+...+5•17=5•(1+2+3+...+17)=5•(17•18):2=5•306:2=1530:2=765

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