1 How much time do you spend playing video gé on weekends

2 Which family owns the largest field for planting crops in the rural area

1 How much time do you spendplaying video games on weekends?

2 Which family owns the largest field for planting crops in the rural area?

1 I enjoy going to the park for a picnic for it allows me to relax in nature

2 We should go to this village in order to explore traditional ways of life

3 If we throw trash on the ground, the environment gets dirty

1 There are too many cars in some cities, and this causes air pollution

2 She is crazy about taking photographs of beautiful landscapes and scenery 

3 The river water is dirty enough to pose threat to aquatic life

1 There are too many cars in some cities, and this causes air pollution.

2 She is crazy about taking photographs of beautiful landscapes and scenery.

3 The river water is dirty enough to pose threat to aquatic life.

1 Avoid touching hot surfaces as they can burn you

2 Are bicycles a popular mode of transport in the countryside

\(B=\dfrac{2x+y}{2x^2-xy}+\dfrac{8y}{y^2-4x^2}+\dfrac{2x-y}{2x^2+xy}\left(x\ne0;y\ne\pm2x\right)\)

\(=\dfrac{2x+y}{x\left(2x-y\right)}-\dfrac{8y}{4x^2-y^2}+\dfrac{2x-y}{x\left(2x+y\right)}\)

\(=\dfrac{\left(2x+y\right)^2}{x\left(2x-y\right)\left(2x+y\right)}-\dfrac{8xy}{x\left(2x-y\right)\left(2x+y\right)}+\dfrac{\left(2x-y\right)^2}{x\left(2x-y\right)\left(2x+y\right)}\)

\(=\dfrac{4x^2+4xy+y^2-8xy+4x^2-4xy+y^2}{x\left(2x-y\right)\left(2x+y\right)}\)

\(=\dfrac{8x^2-8xy+2y^2}{x\left(2x-y\right)\left(2x+y\right)}\)

\(=\dfrac{2\left(4x^2-4xy+y^2\right)}{x\left(2x-y\right)\left(2x+y\right)}\)

\(=\dfrac{2\left(2x-y\right)^2}{x\left(2x-y\right)\left(2x+y\right)}\)

\(=\dfrac{2\left(2x-y\right)}{x\left(2x+y\right)}\)

\(=\dfrac{4x-2y}{2x^2+xy}\)

Với \(x\ne0;y\ne\pm2x\), xét: \(x=\dfrac{1}{2};y=-\dfrac{3}{2}\left(tmdk\right)\)

Thay \(x=\dfrac{1}{2};y=-\dfrac{3}{2}\) vào \(B\), ta được:

\(B=\dfrac{4\cdot\dfrac{1}{2}-2\cdot\dfrac{-3}{2}}{2\cdot\left(\dfrac{1}{2}\right)^2+\dfrac{1}{2}\cdot\dfrac{-3}{2}}=\dfrac{5}{-\dfrac{1}{4}}=-20\)

\(Toru\)

\(P_{Fe}=V_{Fe}.D_{Fe}=100.18000=1800000\left(N\right)\)

\(n_{FeO}=\dfrac{2,16}{72}=0,03\left(mol\right)\\ n_{HCl}=0,2.0,4=0,08\left(mol\right)\\ a,PTHH:FeO+2HCl\rightarrow FeCl_2+H_2O\\ Vì:\dfrac{0,03}{1}< \dfrac{0,08}{2}\Rightarrow HCldư\\ n_{FeCl_2}=n_{FeO}=0,03\left(mol\right)\\ m_{FeCl_2}=127.0,03=3,81\left(g\right)\\ n_{HCl\left(Dư\right)}=0,08-2.0,03=0,02\left(mol\right)\\ V_{ddsau}=V_{ddHCl}=0,4\left(l\right)\\ C_{MddHCl\left(dư\right)}=\dfrac{0,02}{0,4}=0,05\left(M\right);C_{MddFeCl_2}=\dfrac{0,03}{0,4}=0,075\left(M\right)\)

\(n_{CuO}=\dfrac{4}{80}=0,05\left(mol\right)\\a, CuO+H_2SO_4\rightarrow CuSO_4+H_2O\\ n_{CuSO_4}=n_{H_2SO_4}=n_{CuO}=0,05\left(MOL\right)\\ b,m_{CuSO_4}=0,05.160=8\left(g\right)\\ c,V_{ddH_2SO_4}=\dfrac{0,05}{0,5}=0,1\left(l\right)\\ d,V_{ddCuSO_4}=V_{ddH_2SO_4}=0,1\left(l\right)\\ C_{MddCuSO_4}=\dfrac{0,05}{0,1}=0,5\left(M\right)\)