\(x^3-3x^2y+3xy^2-y^3\)

\(=x^3-3\cdot x^2\cdot y+3\cdot x\cdot y^2-y^3\)

\(=\left(x-y\right)^3\)

Thay x=3 và y=2 vào ta có:

\(\left(3-2\right)^3=1^3=1\)

1 Sue wishes she hadn't bought that new book

2 Unless you walk faster, you will be late

3 Carol spent 2 hours fixing the television sets

4 I make these handicrafts by myself 

5 If I were you, I would take the bus instead of the train

II

1 She doesn't have to get up early on Saturday

2 Children mustn't be left alone in car

3 John must explain this if he want his student to succeed

4 I have to file the report this week

5 We don't have to work overtime on Saturdays

6 You mustn't drive more than 25 mph in this zone

7 She didn't have to attend the presentation yesterday

8 She has to pick up her children at school

9 You don't have to arrive before 8

10 They had to visit the doctor yesterday as they didn't feel well

53−3(x+4)=32

\(^{3^2}\).\(^{3^3}\)+\(2^3\).\(2^2\)

(\(^{2^3}\).\(^{3^3}\))+(\(2^2\).​\(^{3^2}\)​​​

=275

a) 1 + 3 + 5 + ... + 13

= (13 + 1).[(13 - 1) : 2 + 1] : 2

= 14 . 7 : 2

= 49

= 7²

b) 3² + 4² + 12²

= 9 + 16 + 144

= 169

= 13²

250 : x + 3.5 = 5^2

=> 250:x = 25 - 15 = 10

=> x = 250 : 10 = 25

cá bạn ơi giúp mình với

Các bạn giúp mình với ạ

Mình làm ngắn gọn nhé.

\(A=1+2+2^2+...+2^{50}\)

\(\Rightarrow2A=2+2^2+...+2^{51}\)

\(\Rightarrow2A-A=2+2^2+...+2^{51}-1-2-2^2-...-2^{50}\)

\(\Rightarrow A=2^{51}-1\)

\(B=1+3+...+3^{66}\)

\(3B=3+3^2+...+3^{67}\)

\(2B=3+3^2+...+3^{67}-1-3-...-3^{66}\)

\(2B=3^{67}-1\)

\(B=\frac{3^{67}-1}{2}\)

\(A=2+2^2+2^3+2^4+...+2^{100}\)

\(=2+\left(2^2+2^3+2^4\right)+...+\left(2^{98}+2^{99}+2^{100}\right)\)

\(=2+2^2\left(1+2+2^2\right)+...+2^{98}\left(1+2+2^2\right)\)

\(=2+7\cdot\left(2^2+2^5+...+2^{98}\right)\)

=>A không chia hết cho 7 mà là chia 7 dư 2 nha bạn