I/know/him/since/we/be/primary students
11 phút trước
Kho 1 chứa số tấn gạo là
`121/(3+8) xx 3 = 33 (tấn)`
Kho 2 chứa số tấn gạo là
`121 - 33 = 88(tấn)`
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Kho 1 chưas 121x3/11=33(tấn)
Kho 2 chứa 121-33=88(tấn)
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tổng số phần `=` nhau là :
`3 + 8 = 11 ( phần)`
kho `1` chứa đc số tấn gạo là :
`121 : 11 xx 3 = 33 (tấn)`
kho `2` chứ đc số tấn gạo là :
`121 - 33 = 88 ( tấn)`
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\(\dfrac{1}{2^2}< \dfrac{1}{1\cdot2}\\ \dfrac{1}{3^2}< \dfrac{1}{2\cdot3}\\ \dfrac{1}{4^2}< \dfrac{1}{3\cdot4}\\ ...\\ \dfrac{1}{50^2}< \dfrac{1}{49\cdot50}\\ \Rightarrow A=\dfrac{1}{1^2}+\dfrac{1}{2^2}+\dfrac{1}{3^2}+\dfrac{1}{4^2}+...+\dfrac{1}{50^2}< 1+\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{49\cdot50}\\ \Rightarrow A< 1+1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{49}-\dfrac{1}{50}\\ \Rightarrow A< 2-\dfrac{1}{50}< 2\)
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`A = 1/1^2 + 1/2^2 + 1/3^2 + 1/4^2 + ... + 1/50^2`
`=> A = 1 + 1/2^2 + 1/3^2 + 1/4^2+ ... + 1/50^2`
ta giữ nguyên `1`:
ta thấy :
`1/2^2 = 1/(2.2) < 1/(1.2)`
`1/3^2 = 1/(3.3) < 1/(2.3)`
`1/4^2 = 1/(4.4) < 1/(3.4)`
`............................................`
`1/50^2 = 1/(50.50) < 1/(49.50)`
`=> A < 1 + 1/(1.2) + 1/(2.3) + .... + 1/(49.50)`
`=> A < 1 + 1 - 1/2 + 1/2 - 1/3 + ... + 1/49 - 1/50`
`=> A < 1 + 1 - 1/50`
`=> A < 2 - 1/50 < 2`
`=> A < 2`
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20 phút trước
`41 - (2.x - 5) = 3^2`
`41 - (2.x - 5) = 9`
`2.x-5=41-9`
`2.x-5=32`
`2.x=32+5`
`2.x=37`
`x=37:2`
`x=18,5`
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\(41-\left(2x-5\right)=3^2=9\)
=> 2x - 5 = 41 - 9 = 32
=> 2x = 32 + 5 = 37
=> x = 37/2
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`41-(2x -5) = 3^2`
`<=> 2x-5 = 41 -3^2 =41-9`
`<=> 2x-5 =32`
`<=> 2x = 32+5=37`
`=> x=37/2`
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44 phút trước
VI . Rewrite the following sentences without changing their original meanings.
-> Your father _____should not drink so much wine_____________________________________
6 . Getting up early every day is good for your health
-> You ___________you get up early every day_____________________________
9 . It's good for you to take exercise every day.
-> You ___________should take exercise every day_____________________________
10 . It's very important not to drink the water there. It will make you ill
-> You ____________should not drink the water there because it will make you ill____________________________
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`2^3 + 2 . { 12 + 2 . [ 3 xx ( 5 - 2) + 1]} + 1`
`=2^3 + 2 . { 12 + 2 . [ 3 xx 3 + 1]} + 1`
`=2^3 + 2 . { 12 + 2 . [ 9 + 1 ]} + 1`
`=2^3 + 2 . { 12 + 2 . 10 +1}`
`=2^3 + 2 . { 12 + 20 + 1}`
` = 2^3 + 2 . 33`
`=8 + 2 . 33`
`= 8 + 66`
`= 74`
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Chúc bạn học tốt !!!
Phần 7) \(5\) : ( \(^{\dfrac{-5}{2}^2}\)) + \(\dfrac{2}{15}.\dfrac{3}{2}\) - ( \(-2018^0\)) = \(5\) : \(\dfrac{25}{4}\) + \(\dfrac{6}{30}\) - \(1\) + \(0,25\)
= \(\dfrac{4}{5}\) + \(\dfrac{1}{5}\) - \(\dfrac{5}{5}\) + \(\dfrac{1}{4}\)
= \(0\) + \(\dfrac{1}{4}\) = \(\dfrac{1}{4}\)
Phần 8) ( \(1,2-\dfrac{1}{2}\) ) : \(1\dfrac{1}{20}\) + \(\dfrac{3}{4}-1,25\) - \(\left(-\dfrac{3}{2}\right)^2\) = \(\dfrac{7}{10}\) \(:\dfrac{21}{20}\) + \(\dfrac{3}{4}\) - \(\dfrac{5}{4}\)
= \(\dfrac{2}{3}\) - \(\dfrac{1}{2}\) = \(\dfrac{4}{6}\) - \(\dfrac{3}{6}\) = \(\dfrac{1}{6}\)
Phần 9) \(\dfrac{\left(-1\right)^6.3^5.4^3}{9^2.2^5}\) = \(\dfrac{1.3^5.2^6}{3^4.2^5}\) = \(3.2=6\)
Phần 10) \(\dfrac{3}{5}+2\dfrac{1}{5}:\left(\dfrac{-1}{2}\right)^3\)- \(1^{2008}\) =
\(\dfrac{3}{5}+\dfrac{7}{5}:\dfrac{-1}{8}-1=\dfrac{3}{5}-\dfrac{56}{5}-\dfrac{5}{5}=\dfrac{3-56-5}{5}=\dfrac{-58}{5}\)
Phần 11) \(12+8.\left(\dfrac{-1}{3}\right)^3+\) \(\left[\left(2018\right)^0:\dfrac{1}{2}\right]^2\) = \(12+8.\dfrac{-1}{27}+2^2\)
= \(12-\dfrac{8}{27}+4=16-\dfrac{8}{27}=\dfrac{424}{27}\)
Phần 12) \(2^3.\left(\dfrac{1}{4}\right)^3-6\dfrac{3}{5}-\dfrac{5}{8}+4\dfrac{3}{5}=8.\dfrac{1}{64}-\dfrac{33}{5}-\dfrac{5}{8}+\dfrac{23}{5}\)
= \(\left(\dfrac{1}{8}-\dfrac{5}{8}\right)-\left(\dfrac{33}{5}-\dfrac{23}{5}\right)\)
= \(\dfrac{-1}{2}-2=\dfrac{-1}{2}-\dfrac{4}{2}=\dfrac{-5}{2}\)
\(CuongDoraemon123\)
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`12/19 . 7/15 . (-13)/17 . 19/12 . 17/13`
`=(12/19 . 19/12) . ( (-13)/17 . 17/13) . 7/15`
`= 1 . (-1) . 7/15`
`= -1 . 7/15`
`=-7/15`
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`12/19 * 7/15 * (-13)/17 * 19/12 * 17/13`
`= (12/19 * 19/12)* ( (-13)/17 * 17/13) * 7/15`
`=1* (-1)* 7/15`
` = (-1) * 7/15 = -7/15`
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