$D\,=2x(10x^2-5x-2)-5x(4x^2-2x-1)\\\quad =20x^3-10x^2-4x-20x^3+10x^2+5x\\\quad =(20x^3-20x^3)+(-10x^2+10x^2)+(-4x+5x)\\\quad =x$

Thay $x=-5$ vào $D=x$

$\Rightarrow D=-5$

Vậy $D=-5$ với $x=-5$

Ta có: \(D=2x\left(10x^2-5x-2\right)-5x\left(4x^2-2x-1\right)\)

\(=20x^3-10x^2-4x-20x^2+10x^2+5x\)

=x=-5

a, 250g = 0,25kg

Trọng lượng là

\(P=10m=10.0,25=2,5\left(N\right)\) 

b, Trọng lượng là

\(P=10m.10.2=20N\) 

c, 2 tấn = 2000kg

Trọng lượng là

\(P=10m=10.2000=20,000N\)

1. D. because
2. A. than
3. B. up
4. C. driver's
5. B. which
6. A. for
7. C. experience
8. D. taken
9. C. All
10. D. part

Rewriting sentences exercise:

1. You should remain inside during disasters.
2. Everybody in my neighborhood has a well-prepared plan for the coming typhoon.
3. I suggest keeping a first aid kit in every bathroom.
4. It is very useful to watch local TV or listen to the radio for more information.
5. If you are not careful, you may fall.
6. I'd rather you kept quiet as I'm very tired.

Sentences using the given words:

1. We have escape plans to save ourselves from disasters.
2. Disasters can make many people homeless.

And lastly, for putting the words in the correct order:

3. I will help you get outside and go to a safe place if you know how to follow an escape plan.
4. A large earthquake or tsunami has started undersea.

Answer:

EX1:

1. because
2. than
3. up
4. driver's
5. which
6. for
7. experience
8. taken
9. All
10. part

EX2:

1.

⇒  You should remain inside during disasters.
2.

⇒ Everybody in my neighborhood has a well-prepared plan for the coming typhoon.
3.

⇒ I suggest keeping a first aid kit in every bathroom.
4.

⇒It is very useful to watch local TV or listen to the radio for more information.
5.

⇒If you are not careful, you may fall.
6.

⇒ I'd rather you kept quiet as I'm very tired.

EX3:

1.

⇒We have escape plans to save ourselves from disasters.
2.

⇒Disasters can make many people homeless.

EX4:

3.

⇒ I will help you get outside and go to a safe place if you know how to follow an escape plan.
4.

⇒ A large earthquake or tsunami has started undersea.

@Darriel

20 announcement

21 carelessly

22 unreasonable  

Bài kiểm tra em nên tự làm nha, viết dù hay hay không cũng là bài của em, em phải viết thì mới biết mình viết được đến đâu được em ạ!

KT mik ko giúp đc bn đâu

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