\(B=26\cdot22+13\cdot23+13\cdot33\)

\(=26\cdot22+13\cdot56\)

\(=26\cdot22+26\cdot28\)

=1300

1300

1300

`@` `\text {Ans}`

`\downarrow`

\(37.(-5)+5.17- ( 13.23+23.17 )\)

`=`\(5\cdot\left(-37+17\right)-23\left(13+17\right)\)

`=`\(5\cdot\left(-20\right)-23\cdot20\)

`=`\(20\cdot\left(-5-23\right)\)

`=`\(20\cdot\left(-28\right)=-560\)

\(13.12+26.17\)

\(=13.12+13.34\)

\(=13\left(12+34\right)\)

\(=13.46\)\(\Leftrightarrow\left(13.23.2\right)⋮13.23\)

Thank nha

Chọn C

13. 23 + 22 − 3. 17 + 28 = 13.45 − 3.45 = 45. 13 − 3 = 45.10 = 450

\(\frac{1}{13}+\frac{3}{13.23}+\frac{3}{23.33}+...+\frac{3}{2303.2306}\)

\(=\frac{3}{39}+\frac{3}{13.23}+\frac{3}{23.33}+...+\frac{3}{2303.2306}\)

\(=\frac{3}{13.3}+\frac{3}{13.23}+\frac{3}{23.33}+...+\frac{3}{2303.2306}\)

\(=1-\frac{1}{13}+\frac{1}{13}-\frac{1}{23}+...+\frac{1}{2303}-\frac{1}{2306}\)

\(=1-\frac{1}{2306}=\frac{2305}{2306}\)

là khoảng cách : 13 - 3 = 10 thì ta cho 10 là mẫu số của 7, bn hiểu ko???

A \(=\frac{7}{3.13}+\frac{7}{13.23}+...+\frac{7}{53.63}=\frac{7}{10}.\left(\frac{10}{3.13}+\frac{10}{13.23}+...+\frac{10}{53.63}\right)\)

   \(=\frac{7}{10}.\left(\frac{1}{3}-\frac{1}{13}+\frac{1}{13}-\frac{1}{23}+...+\frac{1}{53}-\frac{1}{63}\right)=\frac{7}{10}.\left(\frac{1}{3}-\frac{1}{63}\right)\)

   \(=\frac{7}{10}.\frac{20}{63}=\frac{2}{9}\)

đúng cái nhé

có ai bảo bn sai đâu ?               

a,  10 x + 2 2 . 5 = 10 2

10x = 100–20

10x = 80

x = 8

b,  5 2 + 15 - x = 30

15–x = 5

x = 10

c,  2 2 . 5 2 - 25 + x = 40

100–(25+x) = 40

25+x = 60

x = 35

d,  7 2 x - 6 2 x = 13 . 2 3 - 26

49x–36x = 104–26

13x = 78

x = 6