\(17x⋮2v\text{à}3\)

\(\Rightarrow17x⋮6\)

\(\Leftrightarrow x⋮\dfrac{17}{6}\)

\(\Rightarrow x\in B\left(\dfrac{17}{6}\right)=\left\{\dfrac{17}{6};\dfrac{17}{3};....\right\}\)

Vì dấu hiệu chia hết cho 2 là các số chẵn; chia hết cho 3 là tổng các chữ số của số đó chia hết cho 3 thì chia hết cho 3; vì 1+7=8 nên x= 4 vì 1+7+4= 12/ 12 chia hết cho 3 và 12 cũng là số chẵn 

4A = 2² + 2⁴ + ...+ 2¹⁰⁰

4A - A = 2¹⁰⁰ - 1

 \(A=\dfrac{2^{100}-1}{3}\) 

5^x.3 + 5^x+1 = 200

5^x.( 3 +5) = 200

5^x = 200: 8

5^x = 25

5^x = 5²

x = 2

a) Ta có : 2³⁰⁰ = ( 2³ )¹⁰⁰ = 8¹⁰⁰

3²⁰⁰ = ( 3² )¹⁰⁰ = 9¹⁰⁰

Vì 8¹⁰⁰ < 9¹⁰⁰ hay 2³⁰⁰ < 3²⁰⁰

b) Ta có : 125⁵ = ( 5³ )⁵ = 5¹⁵

25⁷ = ( 5² )⁷ = 5¹⁴

Vì 5¹⁵ > 5¹⁴ nên 125⁵ > 25⁷

Exercise 2:

1. I started taking part in English club in April.

=> I have taken part in English club since April. 

2. My sister began teaching English 20 years ago.

=> The first time my sister taught English was 20 years ago. 

3. It began to rain half an hour ago.

=> It has been raining for half an hour. 

4. They began to build this hotel a year ago.

=> They have built this hotel for a year. 

5. He has had his breakfast since 7 o’clock.

=> He began having his breakfast at 7 o’clock.

6. Mr. Ba has talked to our teacher for an hour.

=> Mr. Ba began talking to our teacher an hour ago. 

7. We started working here since August

=> The first time we worked here was in August. 

8. I started writing this report a week ago.

=> I have written this report for a week. 

1: I started being a member of the English club in April.

2: The first time my sister began teaching English was 20 years ago.

3: It started raining half an hour ago.

4: They have been building this hotel for a year.

5: He had his breakfast at 7 o'clock

6: Mr.Ba began talking to our teacher an hour ago

7: The first time I started working here was August

8: I have been writing this report for a week

dễ thế này mà.

giúp mình bài toán trên nhé