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\(B=26\cdot22+13\cdot23+13\cdot33\)
\(=26\cdot22+13\cdot56\)
\(=26\cdot22+26\cdot28\)
=1300
`@` `\text {Ans}`
`\downarrow`
\(37.(-5)+5.17- ( 13.23+23.17 )\)
`=`\(5\cdot\left(-37+17\right)-23\left(13+17\right)\)
`=`\(5\cdot\left(-20\right)-23\cdot20\)
`=`\(20\cdot\left(-5-23\right)\)
`=`\(20\cdot\left(-28\right)=-560\)
\(13.12+26.17\)
\(=13.12+13.34\)
\(=13\left(12+34\right)\)
\(=13.46\)\(\Leftrightarrow\left(13.23.2\right)⋮13.23\)
Chọn C
13. 23 + 22 − 3. 17 + 28 = 13.45 − 3.45 = 45. 13 − 3 = 45.10 = 450
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
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
\(=\frac{3}{3.13}+\frac{3}{13.23}+...+\frac{3}{1993.2003}\)
\(=\frac{1}{10}.\left(1-\frac{3}{13}+\frac{3}{13}-\frac{3}{23}+...+\frac{3}{1993}-\frac{3}{2003}\right)\)
\(=\frac{1}{10}.\left(1-\frac{3}{2003}\right)\)
\(=\frac{1}{10}.\frac{2000}{2003}\)
\(=\frac{200}{2003}\)
Đặt \(A=\frac{1}{13}+\frac{3}{13.23}+\frac{3}{23.33}+...+\frac{3}{1993.2003}\)
\(\Rightarrow A=\frac{3}{3.13}+\frac{3}{13.23}+\frac{3}{23.33}+...+\frac{3}{1993.2003}\)
\(\Rightarrow A=3\left(\frac{1}{3.13}+\frac{1}{13.23}+\frac{1}{23.33}+...+\frac{1}{1993.2003}\right)\)
\(\Rightarrow A=\frac{3}{10}\left(\frac{10}{3.13}+\frac{10}{13.23}+\frac{10}{23.33}+...+\frac{10}{1993.2003}\right)\)
\(\Rightarrow A=\frac{3}{10}\left(\frac{1}{3}-\frac{1}{13}+\frac{1}{13}-\frac{1}{23}+\frac{1}{23}-\frac{1}{33}+...+\frac{1}{1993}-\frac{1}{2003}\right)\)
\(\Rightarrow A=\frac{3}{10}\left(\frac{1}{3}-\frac{1}{2003}\right)\)
\(\Rightarrow A=\frac{3}{10}.\left(\frac{2003}{6009}-\frac{3}{6009}\right)\)
\(\Rightarrow A=\frac{3}{10}.\frac{2000}{6009}\)
\(\Rightarrow A=\frac{200}{2003}\)
12.23 - 13.17 - (13.23 + 13.17)
= 12.23 - 13.17 - 13.23 - 13.17
=( 12.23 - 13.23) - ( 13.17 + 13.17)
= - 13.17 . 2
= - 442
\(13.23-13.17-\left(13.23+13.17\right)\)
\(=13.23-13.17-13.23-13.17\)
\(=13.23-13.23-13.17-13.17\)
\(=0-2.13.17\)
\(=-442\)