110,5:34=3,25

905,2:7,3=124

483:35=13,8

91,08:3,6=25,3

3:6,25=0,48

\(A=\frac{1}{1.3}+\frac{1}{3.5}+....+\frac{1}{21.23}\)

A=\(\frac{1}{3}\left(1-\frac{1}{3}+\frac{1}{3}-.......-\frac{1}{23}\right)\)=\(\frac{1}{3}.\frac{22}{23}=\frac{22}{69}\)

hok t

tl lại

\(A=\frac{1}{1.3}+....\frac{1}{21.23}\)

\(A=\frac{1}{2}\left(1-\frac{1}{3}+.....+\frac{1}{21}-\frac{1}{23}\right)\)

\(A=\frac{1}{2}.\frac{22}{23}=\frac{11}{23}\)

k t nha

\(\frac{1}{3}+\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+...+\frac{1}{483}\)

\(=\frac{1}{1\times3}+\frac{1}{3\times5}+\frac{1}{5\times7}+\frac{1}{7\times9}+...+\frac{1}{21\times23}\)

\(=\frac{1}{2}\times[2\times\left(\frac{1}{1\times3}+\frac{1}{3\times5}+\frac{1}{5\times7}+\frac{1}{7\times9}+...+\frac{1}{21\times23}\right)]\)

\(=\frac{1}{2}\times\left(\frac{2}{1\times3}\times\frac{2}{3\times5}+\frac{2}{5\times7}+\frac{2}{7\times9}+...+\frac{2}{21\times23}\right)\)

\(=\frac{1}{2}\times\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{21}-\frac{1}{23}\right)\)

\(=\frac{1}{2}\times\left(1-\frac{1}{23}\right)\)

\(=\frac{1}{2}\times\frac{22}{23}\)

\(=\frac{11}{23}\)

Nhớ h cho mk nha

45,3 + 54,68 = 99,98

98 - 72,6 = 25,4

6,25 * 35 = 218,75

Bạn tính máy tính luôn cho nhanh ,cần gì phải hỏi

45,3 - 54,68 = -9,63

98 - 72,6 = 25,4

6,25 x 35 = 218,75

 E=4/3+4/15+4/35+4/63+...+4/399+4/483

=4/1.3+4/3.5+4/5.7+4/7.9+...+4/19.21+4/21.23

=2(2/1.3+2/3.5+2/5.7+...+2/19.21+2/21.23)

=2(1/1-1/3+1/3-1/5+1/5-1/7+...+1/19-1/21+1/21-1/23)

=2(1/1-1/23)

=2(23/23-1/23)

=2.22/23

=44/23

Đặt biểu thực là A

2A = \(\dfrac{2}{1.3}+\dfrac{2}{3.5}+\dfrac{2}{5.7}+\dfrac{2}{7.9}+...+\dfrac{2}{21.23}\)

= \(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+...+\dfrac{1}{21}-\dfrac{1}{23}=1-\dfrac{1}{23}=\dfrac{22}{23}\)

=> A = \(\dfrac{11}{23}\)

266,22 : 34= 7,83

483 : 35 = 13,8

91,08 : 3,6 = 25,3

3 : 6,25 = 0,48

cam on ban nhe

266.22 / 34 = 7.83

483 / 35 = 13.8

91.08 / 3.6 = 25.3

3 / 6.25 = 0.48

483 : 35 = 13.8

k mk nha