Bài 5: 

\(\widehat{BKC}=180^0-\left(\widehat{KBC}+\widehat{KCB}\right)\)

\(=180^0-\dfrac{180^0-80^0}{2}\)

\(=180^0-50^0=130^0\)

2. He prefers listening to pop music over watching TV after school.

3. It's very interesting to make crafts or collect things like stamps and coins.

4. We enjoy visiting museums in our leisure time.

5. I hate getting up early and preparing breakfast in the cold winter days.

6. Vinh enjoys hanging out with friends very much.

7. It is interesting to play beach games.

8. It is better to avoid spending too much time on computer games.

9. My parents wants me to learn something interesting.

10.Jenny dislikes reading poetry.

Bài 4:

Vì  \(\left\{{}\begin{matrix}AB=AC\\BM=MC\\AM.chung\end{matrix}\right.\) nên \(\Delta AMB=\Delta AMC\left(c.c.c\right)\)

Do đó \(\left\{{}\begin{matrix}\widehat{AMB}=\widehat{AMC}\\\widehat{MAB}=\widehat{MAC}\end{matrix}\right.\)

Mà \(\widehat{AMB}+\widehat{AMC}=180^0\) nên \(\widehat{AMB}=\widehat{AMC}=90^0\) hay AM⊥BC

\(\widehat{MAB}=\widehat{MAC}\) (cm trên) nên AM là pg góc BAC

Bài 1:

\(=\dfrac{2\left(x-2\right)-\left(x+2\right)}{\left(x-2\right)\left(x+2\right)}=\dfrac{x-6}{x^2-4}\)

Bài 2:

\(=\dfrac{\left(x-3\right)^2}{x-2}.\dfrac{2\left(x^2-4\right)}{2\left(x-3\right)}=\dfrac{\left(x-3\right)\left(x-2\right)\left(x+2\right)}{x-2}=\left(x-3\right)\left(x+2\right)=x^2-x-6\)

a) 4x² + 4xy + y² = (2x + y)²

c) 8a³ - 36a²b + 54ab² - 27b² = (2a - 3b)³

d) 8x³ + 12x²y + 6xy² + y³ = ( 2x - y)³

A. đô trưởng

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 

1: Xét ΔOAD và ΔOCB có

OA=OC

\(\widehat{O}\) chung

OD=OB

Do đó: ΔOAD=ΔOCB

Suy ra: AD=CB

a: Xét ΔBAH vuông tại A và ΔBDH vuông tại D có

BH chung

\(\widehat{ABH}=\widehat{DBH}\)

Do đó: ΔBAH=ΔBDH