44. If you recycle, you will save natural resources

45. If I knew how to use this machine, I could help you

46. The students were excited about the journey

47. Peter who can solve this diffcult problem is the best student

48. My secretary is a fast typer

a) \(n_{H_2}=\dfrac{0,56}{22,4}=0,025\left(mol\right)\)

\(n_{Cl_2}=\dfrac{1,4}{22,4}=0,0625\left(mol\right)\)

PTHH: Fe + 2HCl --> FeCl₂ + H₂

           0,025<------0,025<--0,025

            2Fe + 3Cl₂ --t^o--> 2FeCl₃

         0,025-->0,0375

             Cu + Cl₂ --t^o--> CuCl₂

         0,025<-0,025

=> \(\left\{{}\begin{matrix}\%m_{Fe}=\dfrac{0,025.56}{0,025.56+0,025.64}.100\%=46,67\%\\\%m_{Cu}=\dfrac{0,025.64}{0,025.56+0,025.64}.100\%=53,33\%\end{matrix}\right.\)

\(\%n_{Fe}=\%n_{Cu}=\dfrac{0,025}{0,025+0,025}.100\%=50\%\)

b) X chỉ chứa FeCl₂

=> %m_FeCl2 = 100%

\(I=100mA=0,1A\)

\(l=200cm=2m\)

Lực từ tác dụng lên dây dẫn:

\(F=B\cdot I\cdot l\cdot sin\alpha\)

\(\Rightarrow F=4\cdot10^{-2}\cdot0,1\cdot2=8\cdot10^{-3}N\)

Ta có: \(x^2-2xy+y^2+1=\left(x-y\right)^2+1\)

Vì \(\left(x-y\right)^2\ge0\forall x,y\)

Mà \(1>0\)

\(\Rightarrow\left(x-y\right)^2+1>0\forall x,y\left(đpcm\right)\)

Những phân số tối giản là: \(\dfrac{1}{3};\dfrac{4}{7};\dfrac{72}{73}\)

Những phân số còn lại chưa tối giản vì:

     \(\dfrac{8}{12}=\dfrac{8:4}{12:4}=\dfrac{2}{3}\)

   \(\dfrac{30}{36}=\dfrac{30:6}{36:6}=\dfrac{5}{6}\)

43 He asked Nga if she lived with her family

44 He asked if my uncle lived in England

45 Mary asked Peter if he would come to her party the day after

46 Mai asked Quang if he phoned her everyweek

47 She asked David if that was his bag

48 She asked me if I had to come back before 10

49 She asked if I was listening to music

50 Mary asked Peter if he wanted her to help him

51 She asked me what it was

52 I asked him if he was from Australia

53 I asked Mr Hoang if he would go to Hue on holiday the next month

54 Mary asked Peter if his sister had a book store in Hue

55 Mr Brown asked if he had to go then

56 Hoa asked me what I was doing then

57 She asked me if I could work on Sundays

58 Nga asked her brother if he was in his room then

59 She asked Tom why he was late that day

60 He asked Linda if he could borrow her pen

61 Hung asked Nga if she met his teacher

52 She asked if my father work there

Messi, who was born in argentina, won the FIFA ballon d'Or 2015

David Cameron, who is the prime minister, has resigned after uk voted to leave the european union

Emily Bronte, who is best known for her only novel"Wuthering heights", was an E novelist and poet

Jane Austen whose most highly praised...., was an E novelist

Melbourne where my uncle lives is very beautiful