1 Thực hiện phép tính:
A=\(\dfrac{1}{15.16}+\dfrac{1}{16.17}+...+\dfrac{1}{2016.2017}\)
B=\(\left(1-\dfrac{1}{2}\right)+\left(1-\dfrac{1}{4}\right)+\left(1-\dfrac{1}{8}\right)+...+\left(1-\dfrac{1}{1024}\right)\)
C=\(\dfrac{1}{5.8}+\dfrac{1}{8.11}+...+\dfrac{1}{101.104}\)
D=\(\dfrac{2}{1.4}+\dfrac{2}{4.7}+\dfrac{2}{7.10}+...+\dfrac{2}{101.104}\)
E=\(\dfrac{5^2}{1.6}+\dfrac{5^2}{6.11}+...+\dfrac{5^2}{101.106}\)
A=1/15-1/16+1/16-1/17+...+1/2016-1/2017
A=1/15-1/2017
A=2002/30255
C=1/3[3/5.8+3/8.11+...+3/101.104]
C=1/3[1/5-1/8+1/8-1/11+...+1/101-1/104]
C=1/3[1/5-1/104]
C=1/3.99/520
C=33/520
D=2/3[3/1.4+3/4.7+.....+3/101.104]
D=2/3[1-1/4+1/4-1/7+.....+1/101-1/104]
D=2/3[1-1/104]
D=2/3.103/104
D=103/156
E=5[5/1.6+5/6.11+.....+5/101.106]
E=5[1-1/6+1/6-1/11+.....+1/101-1/106]
E=5[1-1/106]
E=5.105/106
E=525/106
\(A=1.\left(\dfrac{1}{15}-\dfrac{1}{16}+.......+\dfrac{1}{2016}-\dfrac{1}{2017}\right)\)
\(A=\dfrac{1}{15}-\dfrac{1}{2017}=\dfrac{2002}{30255}\)
\(C=\dfrac{1}{3}.\left(\dfrac{1}{5}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{11}+...+\dfrac{1}{101}-\dfrac{1}{104}\right)\)
\(C=\dfrac{1}{3}.\left(\dfrac{1}{5}-\dfrac{1}{104}\right)=\dfrac{1}{3}.\left(\dfrac{99}{520}\right)=\dfrac{99}{2600}\)
mink nghĩ vậy, nhưng câu khác các bạn đã làm rồi nên không làm
cho mink sửa lại phần C
\(\dfrac{1}{3}.\left(\dfrac{99}{520}\right)=\dfrac{33}{520}\)
mink sửa chỗ đó nha
