a: Gọi O là trung điểm của CD

=>O là tâm đường tròn đường kính CD

Xét (O) có

ΔCED nội tiếp

CD là đường kính

Do đó: ΔCED vuông tại E

=>\(\hat{CED}=90^0\)

Xét tứ giác ABCE có \(\hat{CAB}=\hat{CEB}=90^0\)

nên ABCE là tứ giác nội tiếp

b: EFDC là tứ giác nội tiếp

=>\(\hat{EFD}+\hat{ECD}=180^0\)

mà \(\hat{EFD}+\hat{AFD}=180^0\) (hai góc kề bù)

nên \(\hat{AFD}=\hat{ACE}\)

Xét ΔAFD và ΔACE có

\(\hat{AFD}=\hat{ACE}\)

góc FAD chung

Do đó: ΔAFD~ΔACE

=>\(\frac{AF}{AC}=\frac{AD}{AE}\)

=>\(AF\cdot AE=AD\cdot AC\)

11 He asked his daughter what kind of sport were you interested in  

12 I asked the neighboor what time your husband left for work 

13) You hate watching violent films , don't you ?

14) They have just repaired the street ìn front of my house,haven't they ?

15) The first TV picture wasn't produced by Baird in 1926,did he ?

16) This kind of shoes was bought last year,didn't she 

My mom asked me how your course took

The man asked me how many students in the class were there 

26.

\(\sqrt{\dfrac{-3}{2a^3}}=\sqrt{\dfrac{-3a}{2a^4}}=\dfrac{1}{a^2}\sqrt{\dfrac{-3a}{2}}\)

Đáp án B

28.

\(\sqrt{\dfrac{a^3}{a}}=\sqrt{a^2}=\left|a\right|=-a\)

Đáp án B

Bài 3: 

a: \(A=\dfrac{3\left(x+4\right)}{\left(x+4\right)\left(x-4\right)}=\dfrac{3}{x-4}\)

b: Để A nguyên thì \(x-4\in\left\{1;-1;3;-3\right\}\)

hay \(x\in\left\{5;3;7;1\right\}\)

Bài 2: 

a: \(=y\left(6x-y\right)\)

b: \(=x\left(y-2\right)+2\left(y-2\right)=\left(y-2\right)\left(x+2\right)\)

c: =(x+2)(x+5)

1 Yes, they do

2 Yes, it is

3 They often buy fruits and flowers from the market and decorate their houses

4 They often visit their family and friends

Câu 1:

Ta có 2x - y = 8 => 2x - y + 9 = 17

Mà 3x + y = 17 => 2x - y + 9 = 3x + y

<=> 9 - y = x + y <=> 9 = x + 2y <=> x = 9 - 2y

Mà 2x - y = 8 => 18 - 4y - y = 8 => 18 - 5y = 8 => y = 2 => x = 5

Giải giúp e câu 3 đc không ạ, em cảm ơn