2) 4x(x-3y)+12(3y-x)

= 4x(x-3y)-12(x-3y)

=(x-3y)(4x-12)

= 4(x-3y)(x-3)

1) x³+2x²-2x-1

=  (x³-1)+(2x²-2x)

= 2x(x-1)(x²+x+1)(x-1)

=2x(x²+x+1)(x-1)²

1.She likes her bedroom because it is clean and tidy.

A.dirty                   B. big                 C. nice         D. messy

2. I usually get up early to do exercise in the morning.

A. have dinner             B. stay up           C. start         D. go to school

3. Hos always helps her mother cook meals for the family. She’s hard – working.

A. lazy                   B. creative         C. kind        D. humorous

4. Things in the city are more expensive than those in the countryside.

A. cheap                B. cheaper          C. modern          D. more modern

H/c có dạng X₂O₃

a) PTK của h/c là 2X+3O=2.31=62

b) 2X+3O=2.31=62

=> 2X + 48=62

=> X=\(\dfrac{62-48}{2}\)

=>X= 7

Tên Liti, kí hiệu Li

c) %X= \(\dfrac{7.100}{62}\)~11.29%

1.c

2.a 

3.c

4.d

5.d

H/c có dạng Na₂YO₃

Theo đề ta có :  23.2+Y+16.3= 2,65.40

                     => 46+Y+48=106

                     => Y= 106-46-48=12

Nguyên tố Y là Cacbon

Theo đề ta có   p+e+n=28=> (p+e)+n=28

                         p+e-n=8=> (p+e)-n=28

Suy ra: p+e= (28+8):2=18

1. A skirt was given to me by my mother.

2. A new idea has been suggested by a boss

3. This bridge was built in 1889

4. He is being questioned by the police at their site

5. Rice was grown in tropical countries.

6. Their car was being washed when I came

7. The broken vase couldn't be repaired

8. A letter is being written in her room now

9. A big cake has been brought to my house

10. English can be spoken fluently by Lan's father.

11. This book was bought in the market near our house.

a)= 2x³-x+5/2

b)= 1/2xy²+1/3x-3/2y

c)= -3xy²+4x²+6x³y

d)= xz²+9/4x²y³-9/2