A= 1/1.2 + 1/2.3 + 1/3.4+...+ 1/99.100
=1-1/2+1/2-1/3+1/3-1/4+...+1/99-1/100
=1-1/100
=99/100
B=1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90 + 1/110
=1/4.5+1/5.6+1/6.7+1/7.8+1/8.9+1/9.10+1/10.11
=1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11
=1/4-1/11
=7/44
L-i-k-e nha bn hiền
A=1/1.2+1/2.3+...+1/99.100
A=1-1/2+1/2-1/3+1/3-...+1/99-1/100
A=1-1/100
A=99/100
Vậy A=99/100
A=1/1.2 + 1/1.3 +...+1/99.100
=(1/1-1/2)+(1/2-1/3)+...+(1/99-1/100)
=1-1/2+1/2-1/3+...+1/99-1/100
=1-1/100
=99/100
B=1/20+1/30+...+1/110
=1/4.5+1/5.6+...+1/10.11
=(1/4-1/5)+(1/5-1/6)+...+(1/10-1/11)
=1/4-1/5+1/5-1/6+...+1/10-1/11
=1/4-1/11
=7/44
A=1/1.2+1/2.3+1/3.4+...+1/99.100
A=1-1/2+1/2-1/3+1/3-1/4+...=1/99-1/100
A=1-1/100
A=99/100
A=1/1-1/2+1/3-1/4+...+1/99-1/100
=1-1/100
=100/100-1/100
=99/100
B=1/20+1/30+1/42+1/56+1/72+1/90+1/110
=1/4.5+1/5.6+1/6.7+1/7.8+1/8.9+1/9.10+1/10.11
=1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11
=1/4-1/11
=11/44-4/44
=7/44
A= 1/1.2+1/2.3+1/3.4+... + 1/99.100
A= 1-1/2+1/2-1/3+1/3-1/4+... + 1/99-1/100
A=1-1/100
A=99/100
B=1/20+1/30+1/42+1/56+1/72+1/90+1/110
B=1/4.5+1/5.6+1/6.7+1/7.8+1/8.9+1/9.10+1/10.11
B=1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11
B=1/4-1/11
B=7/44
Vậy các cậu Ơi cho mình hỏi:1+1=mấy
=1-1/2+1/2-1/3+1/3-1/4+......+1/99-1/100
=1-1/100
=99/100
7/44 ha
Có làm thì mới có ăn. Những cái loại không làm mà đòi có ăn, là ăn đầu b** với ăn cứt nhá...Đấy nói vậy đi cho dễ hiểu.
\(\sqrt[]{\frac{ }{ }\hept{\begin{cases}\\\\\end{cases}}\orbr{\begin{cases}\\\end{cases}}^2_{ }\sinh\cos\sin\leftarrow\approx}\)