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ngolemai
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1, Tính: 1^3+2^3+3^3+...+n^3
2,1/(4.9)+1/(9.14)+1/(14.19)+...+1/44.49).(1-3-5-7-...-49)/98
3, Biết 13+23+33+...+103=3025. Tính S=23+43+63+...+203
4, Tính: (1/2+1/3+1/4+...+1/2012)/(2011/1+2010/2+2009/3+...+1/2011)
5,CMR:a/ S=1-1/2^2-1/3^2-1/4^2-...-1/2004^2>1/2004
b/ A=1/2^2-1/2^4+1/2^6-...+1/2^(4n-2)-1/2^4n+...+1/2^2002-1/2^2004<0,2
Mọi người giúp mình với, cảm ơn nhìu!!!!





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2,1/(4.9)+1/(9.14)+1/(14.19)+...+1/44.49).(1-3-5-7-...-49)/98
3, Biết 13+23+33+...+103=3025. Tính S=23+43+63+...+203
4, Tính: (1/2+1/3+1/4+...+1/2012)/(2011/1+2010/2+2009/3+...+1/2011)
5,CMR:a/ S=1-1/2^2-1/3^2-1/4^2-...-1/2004^2>1/2004
b/ A=1/2^2-1/2^4+1/2^6-...+1/2^(4n-2)-1/2^4n+...+1/2^2002-1/2^2004<0,2
Mọi người giúp mình với, cảm ơn nhìu!!!!