8: 7/5=(7a-21)/(5a-15)

(7a-31)/(5a-15)=(7a-31)/(5a-15)

3:

a: OA và OC là hai tia đối nhau

=>O nằm giữa A và C

=>AC=OA+OC=5+5=10cm

OA và OB là hai tia đối nhau

=>O nằm giữa A và B

=>AB=AO+BO=5+8=13cm

AC<AB

=>C nằm giữa A và B

=>AC+CB=AB

=>BC=3cm

b: O nằm giữa A và C

OA=OC

=>O là trung điểm của AC

1.C 2.B 
Chúc bạn học tốt

II.

1.C

2.B

3.B

4.D

5.D

6.C

7.D

8.A

9.A

10.D

11.A

12.C

13.C

14.C

15.D

One day, a few of my friends and I went on a picnic to Minyak Beku, a small interesting place on the coast of Malaya.

Minyak Beku is about five miles from Batu Pahat, a well known town in the state of Johore in Malaya. There is a small ancient fort at the entrance to Minyak Beku. The beach at Minyak Beku is beautiful, and there is an iron mine near by.

We arrived at that place in the morning. After getting out of the bus, we separated into different groups and looked for shady places to spend the day.

Soon, most of us went swimming. While in the water, we were playing a few interesting games. Those who were on the beach were playing other games. Some of them even sang songs and danced. There were still others who were interested in nothing, except picking shells.

In short, everyone enjoyed the trip. In the evening, we returned home in our bus, thinking of the fun we had had at that place. I enjoyed the trip so much.

3

Vậy 3

Lời giải:

$(4x-3)-(x+5)=3(10-x)$

$4x-3-x-5=30-3x$

$3x-8=30-3x$

$3x+3x=30+8$

$6x=38$

$x=\frac{38}{6}=\frac{19}{3}$

Có: x² - 3x + 2 = 0 => x² - x - 2x + 2 = 0 => x.(x - 1) - 2.(x - 1) = 0 => (x - 1).(x - 2) = 0 => x - 1 = 0 => x = 1 hoặc x - 2 = 0 => x = 2

Vậy x = {1;2}

=(4^3)^4.(4^2)^5:4^20

=4^12.4^10:4^20

=4^12+10-20

=4^2=16

64⁴ . 16⁵ : 4²⁰

= ( 4³ )⁴ . ( 4²)⁵ : 4²⁰

= 4¹² . 4¹⁰ : 4²⁰

= 4 ^12+10-20

= 4²

64⁴ . 16⁵ : 4²⁰

= 4²