1,2 = 12/10 -> (b) nhé

2/10 nha là câu B đó

Bài 1:

a) \(\Leftrightarrow x^2-8x+16-x^2+4=6\\ \Leftrightarrow-8x=-14\\ \Leftrightarrow x=\dfrac{7}{4}\)

b) \(\Leftrightarrow\left(x^2-1\right)^2=0\\ \Leftrightarrow\left(x-1\right)^2\left(x+1\right)^2=0\\ \Leftrightarrow\left[{}\begin{matrix}x-1=0\\x+1=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=1\\x=-1\end{matrix}\right.\)

c) \(\Leftrightarrow\left[{}\begin{matrix}3x-1=x+2\\3x-1=-x-2\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}2x=3\\4x=-1\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=-\dfrac{1}{4}\end{matrix}\right.\)

Bài 2:

a) \(=5\left(x^2-2xy+y^2-4z^2\right)=5\left[\left(x-y\right)^2-\left(2z\right)^2\right]=5\left(x-y-2z\right)\left(x-y+2z\right)\)

b) \(=\left(x+1\right)^3-\left(3z\right)^3=\left(x-3z+1\right)\left[\left(x+1\right)^2+3z\left(x+1\right)+\left(3z\right)^2\right]=\left(x-3z+1\right)\left(x^2+2x+1+3xz+3z+9z^2\right)\)

c) \(=x\left(x^2-16\right)-15x\left(x-4\right)=x\left(x+4\right)\left(x-4\right)-15x\left(x-4\right)=\left(x-4\right)\left(x^2+4x-15x\right)=\left(x-4\right)\left(x^2-11x\right)=x\left(x-4\right)\left(x-11\right)\)

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

a)Ta có: \(\text{87 - 218 = (23)7 - 218 = 221 – 218 = 217.( 24 -2)= 217.(16 - 2) = 24.14 ⋮ 14}\)
 

Bài 5: 

e: \(\dfrac{2}{x+1}=\dfrac{2x^2-2x+2}{\left(x+1\right)\left(x^2-x+1\right)}\)

\(\dfrac{3}{x^2-x+1}=\dfrac{3x+3}{\left(x+1\right)\left(x^2-x+1\right)}\)

Bài đó ổn rồi ạ nhưng mà câu cuối là breathable nhé