đáp án:307/1830

=1/3.3(1/2.5-1/5.8-1/8.11-...-1/302.305)

=1/3.(3/2.5-3/5.8-3/8.11-...-3/302.305)

=1/3(1/2-1/5-1/5-1/8-1/8-1/11-...-1/302-1/305)

=1/3[(1/2-1/305)+(1/5-1/5)+...+(1/302-1/302)

=1/3*(1/2-1/305)=1/3*(305/610-1/610)=1/3*304/610=152/915

hình như mình làm sai hoặc sai đề , sao số lớn ghê

C=1-2+2²-2³+....+2¹⁰⁰

D=1/5-1/5²+1/5³+.....+1/5¹⁰¹

E=4/2.5+4/5.8+..........+4/302.305

C=1-2+2²-2³+....+2¹⁰⁰

D=1/5-1/5²+1/5³+.....+1/5¹⁰¹

E=4/2.5+4/5.8+..........+4/302.305

Không hiểu chút gì

A= 3/2.5 + 3/5.8 + ....+ 3/302.305
     A= 5-2/2.5 + 8-5/5.8 + ... + 305-302/ 302.305
=> A = 1/2 - 1/5 + 1/5 - 1/8 + ...+ 1/302  - 1/305 
   => A= 1/2 - 1/305
=> A = 303/610
    Vậy A= 303/610.
  Học Tốt !!!

\(A=\frac{3}{2,5}\)\(+\frac{3}{5,8}\)\(+.....+\frac{3}{302,305}\)

\(A=\)\(\frac{5-2}{2,5}\)\(+\frac{8-5}{5,8}\)\(+.......+\)\(\frac{305-302}{302,305}\)

\(\Rightarrow A=\)\(\frac{1}{2}-\frac{1}{5}+\frac{1}{5}\)\(-\frac{1}{8}+.....+\)\(\frac{1}{302}-\frac{1}{305}\)

\(\Rightarrow A=\frac{1}{2}-\frac{1}{305}\)

\(\Rightarrow A=\frac{303}{610}\)

Đề hình như bị sai ban ơi sửa lại

\(A=\dfrac{3}{2.5}+\dfrac{3}{5.8}+\dfrac{3}{8.11}+...+\dfrac{3}{92.95}\)

\(A=3\left(\dfrac{1}{2.5}+\dfrac{1}{5.8}+\dfrac{1}{8.11}+...+\dfrac{1}{92.95}\right)\)

\(A=3.\dfrac{1}{3}\left(\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{11}+...+\dfrac{1}{92}-\dfrac{1}{95}\right)\)

\(A=\dfrac{1}{2}-\dfrac{1}{95}\)

\(A=\dfrac{93}{190}\)

\(B=\dfrac{2}{2.5}+\dfrac{2}{5.8}+\dfrac{2}{8.11}+...+\dfrac{2}{92.95}\)

\(3B=2\left(\dfrac{1}{2.5}+\dfrac{1}{5.8}+\dfrac{1}{8.11}+...+\dfrac{1}{92.95}\right)\)

\(3B=2.\left(\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{11}+...+\dfrac{1}{92}-\dfrac{1}{95}\right)\)

\(3B=2\left(\dfrac{1}{2}-\dfrac{1}{95}\right)\)

\(3B=2.\dfrac{93}{190}\)

\(3B=\dfrac{93}{95}\)

\(\Rightarrow B=\dfrac{31}{95}\)

A=2/2.5+2/5.8+2/8.11+...+2/95.98

=2/3.(3/2.5+3/5.8+3/8.11+...+3/95.98)

=2/3.(1/2-1/5+1/5-1/8+1/8-1/11+...+1/95-1/98)

=2/3.(1/2-1/98)

=2/3.24/49

=16/49

VẬY A=16/49

\(\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}+...+\frac{1}{302.305}\)

=\(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{302}-\frac{1}{305}\)

=\(\frac{1}{5}-\frac{1}{305}\)

=\(\frac{12}{61}\)

tick cho mik nha

S= 2³/2.5+2³/5.8+....................+2³/53.56

S=8/2.5+8/5.8+8/8.11+.......+8/53.56

S=8/3.(3/2.5+3/5.8+3/8.11+...........+3/53.56)

S=8/3.(1/2-1/5+1/5-1/8+1/8-...........+1/53-1/56)

S=8/3.(1/2-1/56)

S=8/3.27/56

S=9/7

nhớ t ick cho mình nha