câu a, \(\dfrac{x}{x+1}\); \(\dfrac{x^2}{1-x}\); \(\dfrac{1}{x^2-1}\)  (đk \(x\)≠ -1; 1)

          \(x^2\) - 1 = ( \(x\) - 1).(\(x\) + 1)

          \(\dfrac{x}{x+1}\) = \(\dfrac{x.\left(x-1\right)}{\left(x+1\right).\left(x-1\right)}\);

          \(\dfrac{x^2}{1-x}\) = \(\dfrac{-x^2}{x-1}\)= \(\dfrac{-x^2.\left(x+1\right)}{\left(x-1\right)\left(x+1\right)}\) 

         \(\dfrac{1}{x^2-1}\)  =  \(\dfrac{1}{\left(x-1\right)\left(x+1\right)}\)

b, \(\dfrac{10}{x+2}\); \(\dfrac{5}{2x-4}\); \(\dfrac{1}{6-3x}\) (đk \(x\) ≠ -2; 2)

    2\(x-4\) = 2.(\(x\) - 2); 6 - 3\(x\) = - 3.(\(x\)  - 2)

   \(\dfrac{10}{x+2}\) = \(\dfrac{10.2.3\left(x-2\right)}{2.3\left(x+2\right)\left(x-2\right)}\) = \(\dfrac{60\left(x-2\right)}{6\left(x-2\right)\left(x+2\right)}\)

    \(\dfrac{5}{2x-4}\) = \(\dfrac{5.3\left(x+2\right)}{2.3\left(x-2\right).\left(x+2\right)}\) = \(\dfrac{15.\left(x+2\right)}{6.\left(x-2\right)\left(x+2\right)}\)

    \(\dfrac{1}{6-3x}\) = \(\dfrac{-1}{3.\left(x-2\right)}\) = \(\dfrac{-1.\left(x+2\right)}{3.2.\left(x-2\right)\left(x+2\right)}\) = \(\dfrac{-2.\left(x+2\right)}{6.\left(x-2\right).\left(x+2\right)}\)

c, \(\dfrac{x}{2x-4}\); \(\dfrac{1}{2x+4}\) và \(\dfrac{3}{4-x^2}\)  đk \(x\) ≠ 2; -2

\(\dfrac{x}{2x-4}\)  =   \(\dfrac{x}{2.\left(x-2\right)}\) = \(\dfrac{x.\left(x+2\right)}{2.\left(x-2\right).\left(x+2\right)}\) 

  \(\dfrac{1}{2x+4}\) = \(\dfrac{1}{2.\left(x+2\right)}\) = \(\dfrac{\left(x-2\right)}{2.\left(x+2\right).\left(x-2\right)}\)

\(\dfrac{3}{4-x^2}\) = \(\dfrac{-3}{\left(x-2\right)\left(x+2\right)}\)  = \(\dfrac{-6}{2.\left(x-2\right)\left(x+2\right)}\)

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

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

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

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