A=1/1.2.3+1/2.3.4+...+1/98.99.100
2A=2/1.2.3+2/2.3.4+...+2/98.99.100
2A=1/1.2-1/2.3+1/2.3-1/3.4+...+1/98.99-1/99.100
2A=1/1.2-1/99.100
2A=1/2-1/9900
2A=4949/9900
A=4949/19800
A=1/1.2.3+1/2.3.4+...+1/98.99.100
2A=2/1.2.3+2/2.3.4+...+2/98.99.100
2A=1/1.2-1/2.3+1/2.3-1/3.4+...+1/98.99-1/99.100
2A=1/1.2-1/99.100
2A=1/2-1/9900
2A=4949/9900
A=4949/19800
A=1/1.2.3+1/2.3.4+....+1/98.99.100
2A=2/1.2-2/2.3.4+...+2/98.99.100
2A=1/1.2-1/2.3+1/2.3-1/3.4+....+1/98.99-1/99.100
2A=1/1.2-1/99.100
2A1/2-1/9900
2A=4949/9900
A=4949/19800
A=1/1.2.3+1/2.3.4+...+1/98.99.100
2A=2/1.2.3+2/2.3.4+...+2/98.99.100
2A=1/1.2-1/2.3+1/2.3-1/3.4+...+1/98.99-1/99.100
2A=1/1.2-1/99.100
2A=1/2-1/9900
2A=4949/9900
A=4949/19800
Trả lời :................................
4949/19800...................
Hk tốt...................................
1/1.2.3=1/1.2-1/2.3
:
:
1/98.99.100=1/98.99-1/99.100
A=1/1.2-1/2.3+1/3.4-1/4.5+...+1/98.99-1/99.100
A=1-1/100
A=99/100
Z = \(\frac{1}{1.2.3}\)+ \(\frac{1}{2.3.4}\) + ... + \(\frac{1}{98.99.100}\)
2Z = \(\frac{1}{1.2}\)- \(\frac{1}{2.3}\)+ \(\frac{1}{2.3}\)- \(\frac{1}{3.4}\)+ ... + \(\frac{1}{98.99}\)- \(\frac{1}{99.100}\)
2Z = \(\frac{1}{1.2}\)- \(\frac{1}{99.100}\)
2Z = \(\frac{4949}{9900}\)
Z = \(\frac{4949}{9900}\)/ 2
Z = \(\frac{4949}{19800}\)
