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2 The meeting will be held before May Day
3 The engine of the car has to be repaired
4 A story is going to be told by the teacher
5 The cake is being cut with a sharp knife by Mary
6 Luckily for me, my name wasn't called
7 His story isn't believed
8 After class, the chalk board is always erased by one of the students
9 The victims have been provided with food and drink
11 Each of us were given 2 exercises books
12 He will be told that news
13 A lot of money was paid me to do the job
14 The window of the laboratory has been changed
a) \(Mg\left(OH\right)_2\) - Magie hidroxit
\(MgCl_2\) - Magie clorua
\(MgS\) - Magie sunfua
\(Mg_3\left(PO_4\right)_2\) - Magie photphat
\(Mg\left(HCO_3\right)_2\) - Magie bicacbonat
1: Xét ΔABD vuông tại A và ΔDAC vuông tại D có
góc ABD=góc DAC
=>ΔABD đồng dạng với ΔDAC
2: ΔABD đồng dạng với ΔDAC
=>BD/AC=AB/DA=AD/DC
=>AD/16=BD/AC=18/DA
=>AD^2=16*18=288
=>AD=12căn 2(cm)
AC=căn AD^2+DC^2=4căn 82(cm)
Câu 10:
\(a,Fe_2O_3+3CO\rightarrow\left(t^o\right)2Fe+3CO_2\\ b,2Al+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2\\ c,2Na+H_2SO_4\rightarrow Na_2SO_4+H_2\\ d,2KOH+H_2SO_4\rightarrow K_2SO_4+2H_2O\\ Fe\left(OH\right)_2+2HCl\rightarrow FeCl_2+H_2O\\ Fe_2\left(SO_4\right)_3+BaCl_2\rightarrow FeCl_2+BaSO_4\left(PTHH.Sai\right)\\ 2Al+3CuSO_4\rightarrow Al_2\left(SO_4\right)_3+3Cu\\ 2Al+3MgO\rightarrow\left(t^o\right)Al_2O_3+3Mg\\ 2Al+3Cl_2\rightarrow\left(t^o\right)2AlCl_3\)
Câu 8,9 đã làm!
Câu 7:
\(\text{Đ}\text{ặt}:N_xO_y\left(x,y:nguy\text{ê}n,d\text{ươ}ng\right)\\ V\text{ì}:\dfrac{m_N}{m_O}=\dfrac{7}{20}\\ \Leftrightarrow\dfrac{14x}{16y}=\dfrac{7}{20}\\ \Rightarrow\dfrac{x}{y}=\dfrac{7.16}{20.14}=\dfrac{2}{5}\\ \Rightarrow x=2;y=5\\ \Rightarrow CTHH:N_2O_5\)
a) \(d\dfrac{CH_4}{kk}=\dfrac{M_{CH_4}}{M_{kk}}=\dfrac{16}{29}< 1\)
⇒ \(CH_4\) nhẹ hơn kk
b) \(d\dfrac{N_2O}{kk}=\dfrac{M_{N_2O}}{M_{kk}}=\dfrac{44}{29}=1,52>1\)
⇒ \(N_2O\) nặng hơn kk
Câu b hỏi khí F2. Có hỏi không khí đâu??
\(15\left(\dfrac{m.}{s}\right)=54\left(\dfrac{km}{h}\right)\)
\(\Rightarrow v_{tb}=\dfrac{s}{\dfrac{\dfrac{1}{2}s}{v'}+\dfrac{\dfrac{1}{2}s}{v''}}=\dfrac{s}{\dfrac{s}{36}+\dfrac{s}{108}}=\dfrac{s}{\dfrac{4s}{108}}=\dfrac{108}{4}=27\left(\dfrac{km}{h}\right)\)
\(TBCv_1-v_2=\left(18+54\right):2=36\left(\dfrac{km}{h}\right)\)
\(\Rightarrow v_{tb}< TBCv_1-v_2\left(27< 36\right)\)
Vậy ta đc đpcm.
25. cleverer nhé (of the 2_ 27. C 29. C (help someone to do/ do sth) 30. D
are saving-are going to buy
listening - reading
are sleeping
makes
will not rain
does not go
to travel
laughing
less => fewer
lately=> late
does it cost => it costs
are => is
four-hours => four-hour
proud
actress
older
II
a)are saving/will buy
b) listening/reading
c)are sleeping
d)makes
e)won't rain
f) isn't going
g)to travel
h)laughing