Bài 1: 

a: =8xy/2x=4y

b: \(=\dfrac{4x-1-7x+1}{3x^2y}=\dfrac{-3x}{3x^2y}=\dfrac{-1}{xy}\)

c: \(=\dfrac{3x-x+6}{2x\left(x+3\right)}=\dfrac{2\left(x+3\right)}{2x\left(x+3\right)}=\dfrac{1}{x}\)

e: \(=\dfrac{5\left(x+2\right)}{4\left(x-2\right)}\cdot\dfrac{-2\left(x-2\right)}{x+2}=\dfrac{-10}{4}=-\dfrac{5}{2}\)

câu 3 bài 1: = (x-y)(y-1)

Mình đang gấp 

Mình đang chuẩn bị đi học rồi, còn 3 phút nữa 

Bài 3: 

Diện tích là:

\(600^2\cdot\dfrac{1}{4}\cdot\dfrac{3}{4}=67500\left(m^2\right)\)

Bài 1.

\(2Fe+3Cl_2\underrightarrow{t^o}2FeCl_3\)

\(Fe_2O_3+3H_2SO_4\rightarrow Fe_2\left(SO_4\right)_3+3H_2O\)

\(H_2SO_4+H_2S\rightarrow2S+2H_2O\)

\(2KMnO_4\underrightarrow{t^o}K_2MnO_4+MnO_2+O_2\)

b: \(=8+2\cdot3-7\cdot1.3+3\cdot\dfrac{5}{4}=8.65\)

Bài 1:
b) \(B=A.\dfrac{-10}{x-4}=\dfrac{x-4}{x+5}.\dfrac{-10}{x-4}=\dfrac{-10}{x+5}\)

Để B nguyên <=> x+5 nguyên mà \(x\in Z\Rightarrow x+5\inƯ\left(-10\right)=\left\{\pm1;\pm2;\pm5;\pm10\right\}\)

\(\Leftrightarrow x\in\left\{-6;-4;-3;-7;0;-10;-15;5\right\}\) kết hợp với điều kiện của x

\(\Rightarrow x\in\left\{-15;-10;-6;-7;-3;0;5\right\}\)

Bài 5:

Có \(\left|x-2018\right|+\left|2x-2019\right|+\left|3x-2020\right|\ge0\) \(\forall\)x

\(\Rightarrow x-2021\ge0\) \(\Leftrightarrow x\ge2021\)

\(\Rightarrow x-2018>0,2x-2019>0,3x-2020>0\)

PT \(\Leftrightarrow x-2018+2x-2019+3x-2020=x-2021\)

\(\Leftrightarrow5x=4036\) \(\Leftrightarrow x=\dfrac{4036}{5}< 2021\) (L)

Vậy pt vô nghiệm

đề là tìm n nguyên để biểu thức nguyên hả bạn ? 

d, \(\frac{3n+1}{n-2}=\frac{3\left(n-2\right)+7}{n-2}=3+\frac{7}{n-2}\)ĐK : \(n\ne2\)

\(\Rightarrow n-2\inƯ\left(7\right)=\left\{\pm1;\pm7\right\}\)

tương tự 

ừ làm hộ tôi nốt hai câu đi

okk, mình nghĩ bạn tự làm tốt hơn, nhưng dạng mới tiếp cận chưa quen nên thôi ;-; 

e, \(\frac{5n}{n+1}=\frac{5\left(n+1\right)-5}{n+1}=5-\frac{5}{n+1}\)ĐK : \(n\ne-1\)

\(\Rightarrow n+1\inƯ\left(5\right)=\left\{\pm1;\pm5\right\}\)

f, \(\frac{n+8}{n+1}=\frac{n+1+7}{n+1}=1+\frac{7}{n+1}\)ĐK : \(n\ne-1\)

\(\Rightarrow n+1\inƯ\left(7\right)=\left\{\pm1;\pm7\right\}\)

I. Write sentences with the cues given

1. Mai / usually / listen / K - pop music / free time.

→ Mai usually listens to K-pop music in her free time.

2. when / I / be / a child / I / enjoy / play / computer games

→ When I was a child, I enjoyed playing computer games.

3. my father / spend / most / spare time / look after / the garden

→ My father spends most of his spare time looking after the garden.

4. watching TV / most / popular / leisure activity / Britain ?

→ Is watching TV the most popular leisure activity in Britain?

5. many teenagers / addicted / the Internet / computer games 

→ Many teenagers are addicted to the Internet and computer games.

6. she / get / hooked / the medical drama / after / watch / the first people 

→ She got hooked on the medical drama after watching the first episode.

7. most / my friends / prefer / play sports / to / surf the net

→ Most of my friends prefer to play sports rather than surf the net.

8. today's world  / teenagers / rely / technology / more / the past 

→ In today's world, teenagers rely on technology more than in the past

II. Write the second sentences so that it has a similar meaning to the first one

1. It takes us more than two hours to see the film " Avatar "

→ The film " Avatar " requires more than two hours of our time to watch.

2. She likes to hang out with friends on Saturday evening

→ She's interested in socializing with friends on Saturday evening