= 0.5 :0.5 -0.25:0.25+0.2:0.2 -0.125:0.125

= 1-1+1-1

=0+ 0

=0 

21. didn’t go

22. isn’t painting

23. aren’t planting

24. Are they making

25. is repairing

26. is taking

27. is explaining

28. is studying

29. tries/ don’t think

30. passes

21. didn’t go

22. isn’t painting

23. aren’t planting

24. Are they making

25. is repairing

26. is taking

27. is explaining

28. is studying

29. tries/ don’t think

30. passes

có ai có thể giúp mình làm bài này đc ko

1 Letters are typed by Mary in the office

2 You will be helped by his father tomorrow

3 Human life has completely been changed by science and technology

4 This bottle was broken by Peter

5 English is being learned in the room

6 Maths will be being studied this time next week 

7 English has been learning by me for 8 years

8 Max's car was being fixed by him from 3 pm to 5 pm yesterday

9 My mind can't be changed

10 I hadn't been told about it

11 He isn't liked

12 Her telephone number isn't known by ,e

13 The children will be brought home by my students

14 I was sent a present last week

15 We were given more information by her 

lm câu 14;16;18;20;22 hả

14)3x-2=2x-3

=>3x-2-2x+3=0

=>x-1=0

=>x=1

16)\(\dfrac{5x+3}{12}\)=\(\dfrac{1+2x}{9}\)

=>\(\dfrac{\left(5x+3\right)x3}{12x3}\)=\(\dfrac{\left(1+2x\right)x3}{9x3}\)

Khử mẫu

=>5x⁴+3x³=x³+2x⁴

=>5x⁴+3x³-x³+2x⁴=0

=>7x⁴+2x³=0

=>x³(7x+2)=0

=>x=0 hoặc 7x+2=0=>x=-2/7

Tất cả k dưới đây đều là \(k\in Z\)

6.

\(\Leftrightarrow\sqrt{3}cot\left(3x-\dfrac{\pi}{3}\right)=1\)

\(\Leftrightarrow cot\left(3x-\dfrac{\pi}{3}\right)=\dfrac{1}{\sqrt{3}}\)

\(\Leftrightarrow cot\left(3x-\dfrac{\pi}{3}\right)=cot\left(\dfrac{\pi}{3}\right)\)

\(\Leftrightarrow3x-\dfrac{\pi}{3}=\dfrac{\pi}{3}+k\pi\)

\(\Leftrightarrow3x=\dfrac{2\pi}{3}+k\pi\)

\(\Leftrightarrow x=\dfrac{2\pi}{9}+\dfrac{k\pi}{3}\) 

7.

\(\Leftrightarrow\sqrt{3}tan\left(3x-15^0\right)=-1\)

\(\Leftrightarrow tan\left(3x-15^0\right)=-\dfrac{1}{\sqrt{3}}\)

\(\Leftrightarrow tan\left(3x-15^0\right)=tan\left(-30^0\right)\)

\(\Leftrightarrow3x-15^0=-30^0+k180^0\)

\(\Leftrightarrow3x=-15^0+k180^0\)

\(\Leftrightarrow x=-3^0+k60^0\)

8.

\(\Leftrightarrow\sqrt{3}cot\left(3x-30^0\right)=1\)

\(\Leftrightarrow cot\left(3x-30^0\right)=\dfrac{1}{\sqrt{3}}\)

\(\Leftrightarrow cot\left(3x-30^0\right)=cot\left(60^0\right)\)

\(\Leftrightarrow3x-30^0=60^0+k180^0\)

\(\Leftrightarrow3x=90^0+k180^0\)

\(\Leftrightarrow x=30^0+k60^0\)

:) chán thật sự 

9. NaHCO3 + HCl → NaCl + H2O + CO2

=> PT ion : \(HCO_3^-+H^+\rightarrow CO_2+H_2O\)

10. NaHCO3 + NaOH → Na2CO3 + H2O

=> PT ion : \(HCO_3^-+OH^-\rightarrow CO_3^{2-}+H_2O\)

11. NH4Cl + NaOH → NH3 + H2O + NaCl

=> PT ion :\(NH_4^++OH^-\rightarrow NH_3+H_2O\)

12. Na2SO4 + FeCl3 -----//---->