a) ( 3x + 2 )( x - 1 ) - ( x + 2 )( 3x + 1 ) = 7

<=> 3x² - x - 2 - ( 3x² + 7x + 2 ) = 7

<=> 3x² - x - 2 - 3x² - 7x - 2 = 7

<=> -8x - 4 = 7

<=> -8x = 11

<=> x = -11/8

b) ( 6x + 5 )( 2x + 3 ) - ( 4x + 3 )( 3x - 2 ) = 8

<=> 12x² + 28x + 15 - ( 12x² + x - 6 ) = 8

<=> 12x² + 28x + 15 - 12x² - x + 6 = 8

<=> 27x + 21 = 8

<=> 27x = -13

<=> x = -13/27 

c) 2x( x + 3 ) - ( x + 1 )( 2x + 1 ) - 5 = 9

<=> 2x² + 6x - ( 2x² + 3x + 1 ) - 5 = 9

<=> 2x² + 6x - 2x² - 3x - 1 - 5 = 9

<=> 3x - 6 = 9

<=> 3x = 15

<=> x = 5

d) ( 5x + 3 )( 4x - 7 ) - ( 10x + 9 )( 2x - 3 ) = 10

<=> 20x² - 23x - 21 - ( 20x² - 12x - 27 ) = 10

<=> 20x² - 23x - 21 - 20x² + 12x + 27 = 10

<=> -11x + 6 = 10

<=> -11x = 4

<=> x = -4/11

a, \(\left(3x+2\right)\left(x-1\right)-\left(x+2\right)\left(3x+1\right)=7\Leftrightarrow-8x-4=7\Leftrightarrow x=-\frac{11}{8}\)

b, \(\left(6x+5\right)\left(2x+3\right)-\left(4x+3\right)\left(3x-2\right)=8\Leftrightarrow27x+21=8\Leftrightarrow x=-\frac{13}{27}\)

c, \(2x\left(x+3\right)-\left(x+1\right)\left(2x+1\right)-5=9\Leftrightarrow3x-6=9\Leftrightarrow x=5\)

d, \(\left(5x+3\right)\left(4x-7\right)-\left(10x+9\right)\left(2x-3\right)=10\Leftrightarrow-11x+6=10\Leftrightarrow x=-\frac{4}{11}\)

 Put in been or gone.

1. Jim is on holiday. he has GONE to Italy
2.Hello ! I've just BEEN to the shops. I've bought lots of things
3.Alice isn't here at the moment. She's GONE to the shop to get a newspaper
4.Tom has GONE out. He'll be back in about an hour
5. 'Are you going to the bank ? "No, I've already BEEN to the bank'

2. been 

3. gone

4. gone

5. been

Complete Bs sentences. Use the verb in brackets + just/already/yet (as sbown).

1. A: Would you something to eat?

B: No, thanks. I've just had lunch. (just/have)

2. A: Do you know where Julia is?

B: Yes, I --- her. (just/see) have just seen 

3. A: What time is David leaving?

B: He --- (already/leave) has already left

4. A: What's in the newspaper today?

B: I don't know. I --- (not/read/yet) haven't read yet

5. A: Is Ann coming to the cinema with us?

B: No, she --- the film. (already/see) has already seen 

6. A: Are your friends here yet? 

B: Yes, they --- (just/arrive)  have just arrived

7. A: What does Tim think about your plan?

B: I --- (not/tell/yet) haven't told yet

áp dụng công thức dãy số cách đều có quy luật bạn

Bạn có thể giải cho mình không vì mai mình học rồi !

( 2x - 1 )( x² - 6x + 15 ) > 0

Ta có : x² - 6x + 15 = ( x² - 6x + 9 ) + 6 = ( x - 3 )² + 6 ≥ 6 > 0 ∀ x

Để bpt > 0 => 2x - 1 > 0

                  => 2x > 1 

                  => x > 1/2

Vậy nghiệm của bất phương trình là x > 1/2

\(\frac{5x+4}{x^2+2x+7}< 0\)

Ta có : x² + 2x + 7 = ( x² + 2x + 1 ) + 6 = ( x + 1 )² + 6 ≥ 6 > 0 ∀ x

Để bpt < 0 => 5x + 4 < 0

                  => 5x < -4

                  => x < -4/5

Vậy nghiệm của bất phương trình là x < -4/5

Dear Chris,
Lots of things have happened since I last wrote to you.
I’ve bought a new car.
 
I / buy / a new car.

My father has started a new job.
 
my father / start / a new job.

I have given up smoking.
 
I / give up / smoking.

Charles and Sarah have gone to Brazil.
 
Charles and Sarah / go / to Brazil.

Suzanne has had a baby.
 
Suzanne / have / a baby.

1. I/buy/a new car

I've bought a new car.

2. my father/start/a new job

My father has started a new job

3. I/give up/smoking

I have given up smoking 

4. Charles and Sarah/go/to Brazil

Charles and Sarah have gone to Brazil 

5. Suzanne/have/a baby

Suzanne has had a baby

( x - 2 )( x - 4 ) + 3

<=> x² - 6x + 8 + 3

<=> ( x² - 6x + 9 ) + 2

<=> ( x - 3 )² + 2 ≥ 2 > 0 ∀ x ( đpcm )

Đề bài mình viết thiếu là CM biểu thức sau không phụ thuộc vào x ( nghĩa là kết quả phải ra số tự nhiên không có x ) 

\(A=\left(2x+1\right)\left(x-1\right)-2x\left(x+2\right)-5\left(-x+3\right)+4\)

\(=2x^2-2x+x-1-2x^2-4x+5x-15+4\)

\(=-12\left(đpcm\right)\)