a: Xét tứ giác AEHF có 

\(\widehat{AEH}=\widehat{AFH}=\widehat{FAE}=90^0\)

Do đó: AEHF là hình chữ nhật

1 How long do you live in HN

2 How often did you go to the movies

3 What did Mrs Robinson buy

4 When was your father in Nghe An

5 How do they go to school

6 Why didn't she go to class

7 Who left home at 7o'clock yesterday

8 What subject does he study in the high school

9 What is your favorite hobby

10 How far is it

\(b,\dfrac{2x}{7x-21}=\dfrac{2x\left(x+3\right)}{7\left(x-3\right)\left(x+3\right)};\dfrac{x+2}{x^2-9}=\dfrac{7\left(x+2\right)}{7\left(x-3\right)\left(x+3\right)}\\ c,\dfrac{3x}{5x^2-30x}=\dfrac{3}{5\left(x-6\right)}=\dfrac{3\left(x-6\right)}{5\left(x-6\right)^2}\\ \dfrac{x+1}{x^2-12x+36}=\dfrac{5\left(x+1\right)}{5\left(x-6\right)^2}\\ d,\dfrac{2x-1}{5x^2+35x}=\dfrac{\left(2x-1\right)\left(x+7\right)}{5x\left(x+7\right)^2};\dfrac{x-2}{x^2+14x+49}=\dfrac{5x\left(x-2\right)}{5x\left(x+7\right)^2}\)

a: y=0; x=3

Bài 1: 

a) 

a: Ta có: \(\dfrac{1}{7}>0\)

mà \(0>\dfrac{9}{-4}\)

nên \(\dfrac{1}{7}>\dfrac{9}{-4}\)

Bài 1: 

a) So sánh:

b)  \(\dfrac{2}{5}=\dfrac{2\cdot7}{5\cdot7}=\dfrac{14}{35}\)

Bài 1: 

b) \(\dfrac{2}{3}=\dfrac{-2}{-3}\)(Vì \(\dfrac{2}{3}=\dfrac{2\cdot\left(-1\right)}{3\cdot\left(-1\right)}=\dfrac{-2}{-3}\))

😟😟