Câu 3: 

a: Áp dụng tính chất của dãy tỉ số bằng nhau, ta được:

\(\dfrac{x}{3}=\dfrac{y}{2}=\dfrac{x+y}{3+2}=\dfrac{90}{5}=18\)

Do đó: x=54; y=36

=2001

a: Xét ΔABC vuông tại B và ΔABE vuông tại B có

AB chung

BC=BE

=>ΔABC=ΔABE

=>góc EAB=góc CAB

=>AB là phân giác của góc EAC

b: Xét ΔAMH vuông tại M và ΔANH vuông tại N có

AH chung

góc MAH=góc NAH

=>ΔAMH=ΔANH

=>AM=AN

=>ΔAMN cân tại A

c: ΔAMH=ΔANH

=>HM=HN

mà HN<HC

nên HM<HC

e: Xét ΔAEC có

AB,CM là đường cao

AB cắt CM tại H

=>H là trực tâm

=>EH vuông góc AC

mà HN vuông góc AC

nên E,H,N thẳng hàng

1,\(\sqrt{\left(x-1\right)^2}=\left|x-1\right|=-\left(x-1\right)=1-x\)

2,\(\sqrt{\left(a-2b\right)^2}=\left|a-2b\right|=-\left(a-2b\right)=2b-a\)

3,\(\sqrt{\left(2x-1\right)^2}=\left|2x-1\right|=2x-1\)

23. What is she doing?

24. What do you usually do after school?

25. What sport does your father like?

26. How often does Minh go swimming?

27. What are they going to do tonight?

28. What does Nga want to go?

29. Where are the children?

30. What do children should do after meals?

31. They often play soccer, table tennis, badminton or swimming

32. They sometimes go swimming

33. In the school music room

34. They usually rehearse plays

35. They often get together and talk about their stamps

36. Yes, most of them enjoy their activities after school hours

lớp mấy vậy

Bài 2: 

a: =>2/3-x=-1/3

hay x=1

b: =>x=-2/5-2/5=-4/5

1. D => bỏ

2. C

3. C

4. A => the

5. A

6. C =>  next

7. C => taught

8. C => the most

9. D => from

10. B => would

II

1. I wish I would become a singer.

2.  She used to walk to school when she was a child.

3. If I were you, I would learn Chinese

4. The man who I met yesterday was my uncle

5. The trees are watered by me everyday

b: \(\Leftrightarrow\left[{}\begin{matrix}x-2=-8\\x-2=8\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-6\\x=10\end{matrix}\right.\)