1 arrived - was still sleeping

2 went - were having

3 was having - stopped

4 arrived - was still sleeping

5 were crossing - saw

8 saw - was standing

9 was sitting - saw

10 were cleaning - came

\(a) S \to SO_2\to H_2SO_3\to Na_2SO_3\to CaSO_3\to Na_2SO_4\\ S + O_2 \xrightarrow{t^o} SO_2\\ SO_2 + H_2O \to H_2SO_3\\ 2NaOH + H_2SO_3 \to Na_2SO_3 + 2H_2O\\ Na_2SO_3 + CaCl_2 \to CaSO_3 + 2NaCl\\ CaSO_3 + 2NaHSO_4 \to CaSO_4 + Na_2SO_4 + SO_2 + H_2O\\ b) CaO \to Ca(OH)_2 \to CaCO_3 \to CaCl_2 \to Ca(NO_3)_2\\ CaO + H_2O \to Ca(OH)_2\\ Ca(OH)_2 + CO_2 \to CaCO_3 +H_2O\\ CaCO_3 + 2HCl \to CaCl_2 +C O_2 + H_2O\\ CaCl_2 + 2AgNO_3 \to 2AgCl + Ca(NO_3)_2\)

\(c) Al \to Al_2O_3\to AlCl_3 \to Al(OH)_3 \to AlCl_3\\ 4Al + 3O_2 \xrightarrow{t^o} 2Al_2O_3\\ Al_2O_3 + 6HCl \to 2AlCl_3 + 3H_2O\\ AlCl_3 + 3KOH \to Al(OH)_3 + 3KCl\\ Al(OH)_3 + 3HCl \to AlCl_3 + 3H_2O\\ d) Fe \to Fe_3O_4\to FeCl_3 \to Fe(OH)_3 \to Fe_2O_3\\ 3Fe + 2O_2 \xrightarrow{t^o} Fe_3O_4\\ Fe_3O_4 + 8HCl \to FeCl_2 + 2FeCl_3 + 4H_2O\\ FeCl_3 + 3KOH \to Fe(OH)_3 + 3KCl\\ 2Fe(OH)_3 \xrightarrow{t^o} Fe_2O_3 + 3H_2O\)

b: =>(x-1)(x+1)+4x(x-1)=0

=>(x-1)(5x+1)=0

=>x=1 hoặc x=-1/5

c: \(\Leftrightarrow2\left(6x+5\right)-10x-3=8x+4x+2\)

=>12x+10-10x-3=12x+2

=>-10x+7=2

=>-10x=-5

hay x=1/2

a: Xét ΔABC vuông tại A và ΔHBA vuông tại H có

góc B chung

Do đó:ΔABC\(\sim\)ΔHBA

Suy ra: AB/HB=BC/BA

hay \(AB^2=HB\cdot BC\)

b: Xét ΔHAC vuông tại H và ΔHBA vuông tại H có

\(\widehat{HAC}=\widehat{HBA}\)

Do đó; ΔHAC\(\sim\)ΔHBA

SUy ra: HA/HB=HC/HA

hay \(HA^2=HB\cdot HC\)

a) Xét ∆ABC(<A=90 ° ) và ∆HBA(<H=90 ° ), ta có:
<B chung ⟹∆ABC~ ∆HBA(g.g)
⟹AB/HB=BC/AB⟹AB*AB=HB*BC hay AB²=BH*BC
b)Xét ∆HAC(<H=90 °) và  ∆HBA(<H=90 ° ), ta được:
<B=<HAC( vì cùng phụ với <BAH do <B+<BAH =90°; <HAC+<BAH =90°)
⟹∆HAC~∆HBA(g.g)
⟹HA/HB=HC/HA⟹HA*HA=HB*HC hayHA²=BH*CH

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