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	20/02/2020 16:15:56
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Tính

A=1/1.2+1/2.3+...+1/99.100
B=3/5.8+3/8.11+...+3/2016.2019
C=1/6.10+1/10.14+...+1/402.406
D=10/7.12+10/12.17+...+10/502.507
E=2^2/1.3+2^2/3.5+...+2^2.2019.2021
2,.
a,7/x+4/5.9+4/9.13+...+4/41.45=29/45
b,5/1.6+5/6.11+...+5/(5x+1)(5x+6)=2019/2020
c,1/3.5+1/5.7+...+1/(2x+1)(2x+3)=15/93