I have known him since we were primary students.

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)`

Kho 1 chưas 121x3/11=33(tấn)

Kho 2 chứa 121-33=88(tấn)

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)`

\(\dfrac{1}{2^2}< \dfrac{1}{1\cdot2}\\ \dfrac{1}{3^2}< \dfrac{1}{2\cdot3}\\ \dfrac{1}{4^2}< \dfrac{1}{3\cdot4}\\ ...\\ \dfrac{1}{50^2}< \dfrac{1}{49\cdot50}\\ \Rightarrow A=\dfrac{1}{1^2}+\dfrac{1}{2^2}+\dfrac{1}{3^2}+\dfrac{1}{4^2}+...+\dfrac{1}{50^2}< 1+\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{49\cdot50}\\ \Rightarrow A< 1+1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{49}-\dfrac{1}{50}\\ \Rightarrow A< 2-\dfrac{1}{50}< 2\)

`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`

`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`

\(41-\left(2x-5\right)=3^2=9\)

=> 2x - 5 = 41 - 9 = 32

=> 2x = 32 + 5 = 37

=> x = 37/2

`41-(2x -5) = 3^2`

`<=> 2x-5 = 41 -3^2 =41-9`

`<=> 2x-5 =32`

`<=> 2x = 32+5=37`

`=> x=37/2`

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____________________________