(3n + 18)$⋮$(n + 2)

=> [(3n + 6) + 12]$⋮(n\; +\; 2)$

$=>\; [3(n\; +\; 2)\; +\; 12]⋮(n\; +\; 2)$

$Vì\; 3(n\; +\; 2)⋮(n\; +\; 2)\; nên\; để\; [3(n\; +\; 2)\; +\; 12]⋮(n\; +\; 2)\; thì\; 12⋮(n\; +\; 2)$

$=>\; n\; +\; 2$∈ Ư(12)

=> n + 2 ∈ {1 ; 2 ; 3 ; 4 ; 6 ; 12}

=> n ∈ {0 ; 1 ; 2 ; 4 ; 10}

Vậy n ∈ {0 ; 1 ; 2 ; 4 ; 10}

Ta có:

\(\overline{abcd}\text{⋮}99\)

\(\Rightarrow\left(100\overline{ab}+\overline{cd}\right)\text{⋮}99\)

\(\Rightarrow\left(99\overline{ab}+\overline{ab}+\overline{cd}\right)\text{⋮}99\)

\(\Rightarrow\left[99\overline{ab}+\left(\overline{ab}+\overline{cd}\right)\right]\text{⋮}99\)

Vì \(99\overline{ab}\text{⋮}99\) và \(\left[99\overline{ab}+\left(\overline{ab}+\overline{cd}\right)\right]\text{⋮}99\)

nên \(\left(\overline{ab}+\overline{cd}\right)\text{⋮}99\) (đpcm)

Điều ngược lại:

\(\left(\overline{ab}+\overline{cd}\right)\text{⋮}99\)

\(\Rightarrow\left(99\overline{ab}+\overline{ab}+\overline{cd}\right)\text{⋮}99\)

\(\Rightarrow\left(100\overline{ab}+\overline{cd}\right)\text{⋮}99\)

\(\Rightarrow\overline{abcd}\text{⋮}99\) (đpcm)

1) What time do classes start? (start)

2) His child washes her face in the morning and in the evening (wash)

3) I am staying in a hotel in HCM City now (stay)

4) Where is your father ? (be)

5 They don't work in the factory. (not/ work)

1) How floors does it has ?

=> How --> How many ; has --> have

2) We have math in tuesday and thursday

=> in --> on

3) She don't have her timetable

=> don't --> doesn't

4) What wills Lan and Nga do after school?

=> wills --> will

Gọi số tự nhiên cần tìm là a (a ∈ N)

Theo bài ra ta có:

a : 6 (dư 2) => (a + 4)$⋮$6

a : 7 (dư 3) => (a + 4)$⋮7$

$a\; :\; 9\; (dư\; 5)\; =>\; (a\; +\; 4)⋮9$

$Và\; a\; là\; số\; nhỏ\; nhất$

$=>\; a\; +\; 4\; =\; BCNN(6,7,9)\; (1)$

$Ta\; có:\; 6\; =\; 2.3\; ;\; 7\; =\; 7\; ;\; 9\; =\; 32$

$=>\; BCNN\; (6,7,9)\; =\; 2.32.7\; =\; 126\; (2)$

$Từ\; (1)\; và\; (2)\; =>\; a\; +\; 4\; =\; 126$

$=>\; a\; =\; 126\; -\; 4$

$=>\; a\; =\; 122$

$Vậy\; số\; tự\; nhiên\; cần\; tìm\; là\; 122$

Ta có:

A = 2 + 2² + 2³ + ... + 2⁶³

A = 2 + (2² + 2³) + ... + (2⁶² + 2⁶³)

A = 2 + 2²(1 + 2) + ... + 2⁶²(1 + 2)

A = 2 + 2².3 + ... + 2⁶².3

A = 2 + (2² + ... + 2⁶²)3

Vì (2² + ... + 2⁶²)3⋮3

2 không chia hết cho 3

nên 2 + (2² + ... + 2⁶²)3 không chia hết cho 3 hay A không chia hết cho 3 (đpcm)

A. Viet: Where is your house, Lan ?

Lan ; My house is on nguyen hue street

Viet ; What is there on the street?

Lan ; There is a hotel , a bookstore, a temple and a police station

Viet; Is your house near the bookstore?

Lan; No, my house isn't near the bookstore

Viet; What is to the left of your house?

Lan ; The police station is to the left of my house

A : Where is your school?

B My school is in the city

A How many students are there in your school?

B There are 1500 students in our school

A What subjects do you have today?

B We have English , Math, and art today

A When do you have literature?

B We have literature on Monday and Thursday

Lan ; Which grade are you in ?

Mai ; I'm in grade six

Lan ; Which class are you in?

Mai: I am in class 6a

A: What do you do after school?

B: I go home and have lunch

A: What do you do in the afternoon?

B: I stay home and do my homework