• 1 Did you really think I wouldn't find out that you went there last night?
• 2 How much time does it usually take you to eat breakfast?
• 3 I wouldn't bet on that horse if I were you.
• 4 My most interesting Canadian friend is Tom.
• 5 There was a traffic accident yesterday morning in front of the house.
• 6 It was Tom that broke the window yesterday.
• 7 Do you think it'll be possible for you to come over and help us this weekend?
• 8 Mary is always acting foolishly.
• 9 The train left the station a few minutes ago.
• 10 “Where did you go?” – “I went to the train station to see a friend.”

1 last night

2 does

3 were

4 is

5 yesterday

6 was

7 Do

8 always

9 ago

10 did

=> I completely agree. English plays a very important role in today’s era of global integration.

ai hỏi ? ( dài quá deck đọc )

dài vậy mom

Each student receives 3 notebooks.  =))

!!!!!!

Olm chào em. Đây là toán nâng cao chuyên đề tính nhanh tổng dãy số có quy luật. Cấu trúc thi chuyên, thi học sinh giỏi các cấp. Hôm nay, Olm sẽ hướng dẫn các em giải chi tiết dạng này như sau:

1.2.3.4 = 1.2.3.4

2.3.4.4 = 2.3.4.(5 - 1) = 2.3.4.5 - 1.2.3.4

3.4.5.4 = 3.4.5.(6 - 2) = 3.4.5.6 - 2.3.4.5

.............................................................................

98.99.100.4 = 98.99.100.(101 - 97) = 98.99.100.101- 97.98.99.100

Cộng vế với vế ta có:

1.2.3.4+2.3.4.4+..+98.99.100.4=98.99.100.101

4.(1.2.3 + 2.3.4 +...+98.99.100) =98.99.100.101

1.2.3+2.3.4+...+98.99.100 = 98.99.100.101:4

1.2.3+2.3.4+...+98.99.100 = 24497550

Ta có: \(1\cdot2\cdot3+2\cdot3\cdot4+\cdots+98\cdot99\cdot100\)

\(=2\left(2-1\right)\left(2+1\right)+3\left(3-1\right)\left(3+1\right)+\cdots+99\left(99-1\right)\left(99+1\right)\)

\(=2\left(2^2-1\right)+3\left(3^2-1\right)+\cdots+99\left(99^2-1\right)\)

\(=\left(2^3+3^3+\cdots+99^3\right)-\left(2+3+\cdots+99\right)\)

\(=\left(1^3+2^3+\cdots+99^3\right)-\left(1+2+3+\cdots+99\right)\)

\(=\left(1+2+3+\cdots+99\right)^2-\left(1+2+3+\cdots+99\right)\)

\(=\left\lbrack99\cdot\frac{100}{2}\right\rbrack^2-99\cdot\frac{100}{2}=\left(99\cdot50\right)^2-99\cdot50\)

=24497550

a) diện tích xung quanh là :

(15+9) x 2 x 6= 288 (c\(m^2\))

b)diện tích toàn phần là :

288 + (15 x 9 ) x 2= 558 (c\(m^2\) )

c) thể tích là :

15 x 9 x 6= 10

A = \(\frac{3}{1.4}\) + \(\frac{3}{4.7}\) + ... + \(\frac{3}{13.17}\)

A = \(\frac11-\frac14+\frac14-\frac17+\cdots+\) \(\frac{1}{13}-\frac{1}{17}\)

A = \(\frac11-\frac{1}{17}\)

A = \(\frac{17}{17}\) - \(\frac{1}{17}\)

A = \(\frac{16}{17}\)

Sửa đề: \(A=\frac{3}{1\cdot4}+\frac{3}{4\cdot7}+\frac{3}{7\cdot10}+\frac{3}{10\cdot13}+\frac{3}{13\cdot16}\)

Ta có: \(A=\frac{3}{1\cdot4}+\frac{3}{4\cdot7}+\frac{3}{7\cdot10}+\frac{3}{10\cdot13}+\frac{3}{13\cdot16}\)

\(=1-\frac14+\frac14-\frac17+\frac17-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+\frac{1}{13}-\frac{1}{16}\)

\(=1-\frac{1}{16}=\frac{15}{16}\)

swimming pool

swimming pool

13 + 4389 + 4

= (11 + 4389) + (2 + 4)

= 4400 + 6

= 4406

4406

xy + 3y + x = 4

xy + 3y + x + 1 = 4 + 1

(xy + 3y) + (x + 1) = 4 + 1

y(x+ 1) + (x+ 1) = 4

(x+ 1)(y + 1) = 4

4 = 2\(^2\); Ư(4) = {-4; - 2; - 1; 1; 2 ; 4}

Lập bảng giá trị ta có:

Theo bảng trên ta có: x; y là:

(x; y) = (-5; -2); (-3; -3); (-2; -5); (0; 3); (1; 1) (3; 0)

Vậy các cặp số nguyên x; y thỏa mãn đề bài là:

(x; y) = (-5; -2); (-3; -3); (-2; -5); (1; 1); (3; 0)

đây là bài toán lớp mấy?