17.x chia hết cho cả 2 và 3
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
4A = 22 + 24 + ...+ 2100
4A - A = 2100 - 1
\(A=\dfrac{2^{100}-1}{3}\)
5x.3 + 5x+1 = 200
5x.( 3 +5) = 200
5x = 200: 8
5x = 25
5x = 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.
\(17x⋮2v\text{à}3\)
\(\Rightarrow17x⋮6\)
\(\Leftrightarrow x⋮\dfrac{17}{6}\)
\(\Rightarrow x\in B\left(\dfrac{17}{6}\right)=\left\{\dfrac{17}{6};\dfrac{17}{3};....\right\}\)
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