`|7-2x|+7=2x`

TH1: `7-2x>=0 <=>x<=7/2`

`7-2x+7=2x`

`x=7/2` (TM)

TH2: `7-2x<0 <=>x>7/2`

`-7+2x+7=2x`

`0x=0`

`=>` PT có nghiệm với mọi `x >7/2`.

Vậy `x>= 7/2`.

`|2x+3|+2x=-4`

TH1: `2x+3 >=0 <=> x>=-3/2`

`2x+3+2x=-4`

`<=> 4x=-7`

`<=>x=-7/4` (L)

TH2: `2x+3 <0 <=>x<-3/2`

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

`<=> -2x-3+2x=-4`

`<=>0x=-1` (VN)

Vậy PTVN.

5. A
6. B

7. B

8. B

4. A

1. A
2. B
3. D
4. D
5. A

Refer:

1. The wheel was invented thousands of years ago.

2. These flowers are watered by my father every morning.

3. Computers are used all over the world.

4. Is a statue of Chu Van An being built ?

5. Fiona was invented to John's party last night.

6. Many ancient things are kept in museums.

7. Is the Temple of Literature surrounded by four busy streets ?

8. Many famous films are made in Hollywood.

9. The dinner is being prepared in the kitchen by her mother.

10. All my homework is done on my computer.

11. Service is included by the bill.

12. The book is chosen carefully by Nana.

13. That room isn't used.

14. Fruits are grown in California.

15. Many young people are attracted by these jeans.

16. This road isn't used very often.

17. The dishes are washed in the evening.

a) `(3/5 x^2 -1/2 y)^2 = (3/5 x^2)^2 - 2. 3/5 x^2 .1/2 y + (1/2 y)^2`

`= 9/25 x^4 - 3/5 x^2y + 1/4 y^2`

1. C

2. D

C1:

`(2/5 +1/2) xx1/4 = (4/10 + 5/10) xx 1/4 = 9/10 xx 1/4 = 9/40`

C2:

`(2/5 +1/2) xx 1/4= 2/5 xx 1/4 +1/2 xx 1/4 = 1/10 + 1/8 = 9/40`