Ta gọi biểu thức đó là D
\(D=\frac{5}{2}\left[\frac{1}{5.8}-\frac{1}{8.11}+....+\frac{1}{302.305}-\frac{1}{305.308}\right]\)
\(D=\frac{5}{2}.\left[\frac{1}{5.8}-\frac{1}{305.308}\right]\)
\(D=\frac{4695}{75152}\)
C=5/58.11+5/8.11.14+3.6/4.5+...+5/302.305.308 CMR C<1/48
Cho B=5/5.8.11+5/8.11.14+...+5/302.305.308
Chứng minh B<1/48
cho c=5/5.8.11+5/8.11.14+5/302.305.308
c/m : c <1/48
Cho C=\(\frac{5}{5.8.11}\)+ \(\frac{5}{8.11.14}\)+..............+\(\frac{5}{302.305.308}\)
Chứng minh C< \(\frac{1}{48}\)
Chứng minh :
1,C=\(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+...+\frac{1}{70}.C< \frac{3}{4}\)
2,D=\(\frac{1}{5^2}+\frac{1}{9^2}+...+\frac{1}{409^2}< \frac{1}{12}\)
3,E=\(\frac{5}{5.8.11}+\frac{5}{8.11.14}+...+\frac{5}{302.305.308}< \frac{1}{48}\)
Cho S=1+2+2^2+2^3+....+2^99
Hãy so sánh S với5*2^98
Tính tổng:A=5/3.9+5/9.15+5/15.21+...+5/63.69
Các bạn giúp mk với ạ!Mk cảm ơn!
A=1/5-2/5^2+3/5^3-4/5^4+...+2019/5^2019-2020/5^2020
Giúp mk vs, mk đag cần gấp
