a) Thể tích của hình hộp chữ nhật đã cho là:

\(V = x \left(\right. x - 1 \left.\right) \left(\right. x + 1 \left.\right) = x^{3} - x\)

b) Tại \(x = 4\), thể tích của hình hộp chữ nhật là:

\(V = 4^{3} - 4 = 60\) (đơn vị thể tích)

Vậy ta có phép chia hết và thương là \(Q = 2 x^{2} - 3 x + 1\).

5x(4x2−2x+1)−2x(10x2−5x+2)=−36 

\(5 x . 4 x^{2} + 5 x . \left(\right. - 2 x \left.\right) + 5 x . 1 + \left(\right. - 2 x \left.\right) . 10 x^{2} + \left(\right. - 2 x \left.\right) . \left(\right. - 5 x \left.\right) + \left(\right. - 2 x \left.\right) . 2 = - 36\) 

\(20 x^{3} + \left(\right. - 10 x^{2} \left.\right) + 5 x + \left(\right. - 20 x^{3} \left.\right) + 10 x^{2} + \left(\right. - 4 x \left.\right) = - 36\)

\(\left(\right. 20 x^{3} - 20 x^{3} \left.\right) + \left(\right. - 10 x^{2} + 10 x^{2} \left.\right) + \left(\right. 5 x - 4 x \left.\right) = - 36\)

\(x = - 36\)

Vậy \(x = - 36\).

a) \(P \left(\right. x \left.\right) + Q \left(\right. x \left.\right)\) 

\(= \left(\right. x^{4} - 5 x^{3} + 4 x - 5 \left.\right) + \left(\right. - x^{4} + 3 x^{2} + 2 x + 1 \left.\right)\)

\(= x^{4} - 5 x^{3} + 4 x - 5 - x^{4} + 3 x^{2} + 2 x + 1\)

\(= \left(\right. x^{4} - x^{4} \left.\right) - 5 x^{3} + 3 x^{2} + \left(\right. 4 x + 2 x \left.\right) + \left(\right. 1 - 5 \left.\right)\)

\(= - 5 x^{3} + 3 x^{2} + 6 x - 4\)

b) \(R \left(\right. x \left.\right) = P \left(\right. x \left.\right) - Q \left(\right. x \left.\right)\)

\(= \left(\right. x^{4} - 5 x^{3} + 4 x - 5 \left.\right) - \left(\right. - x^{4} + 3 x^{2} + 2 x + 1 \left.\right)\)

\(= x^{4} - 5 x^{3} + 4 x - 5 + x^{4} - 3 x^{2} - 2 x - 1\)

\(= \left(\right. x^{4} + x^{4} \left.\right) - 5 x^{3} - 3 x^{2} + \left(\right. 4 x - 2 x \left.\right) + \left(\right. - 1 - 5 \left.\right)\)

\(= 2 x^{4} - 5 x^{3} - 3 x^{2} + 2 x - 6\)

Số tiền 3 quyển sách là:

\(3.120 000 = 360 000\) (đồng)

Số tiền Lan phải trả khi có thẻ thành viên là:

\(360 000. \left(\right. 100 \% - 10 \% \left.\right) = 324 000\) (đồng)

Ta có: \(350 000 - 324 000 = 26 000\) (đồng).

Do đó Lan được trả lại \(26 000\) đồng.​

​Ta có: \(1^{2} + 2^{2} + 3^{2} + \ldots + 1 0^{2} = 385\)

Suy ra: \(\left(\right. 1^{2} + 2^{2} + 3^{2} + \ldots + 1 0^{2} \left.\right) . 3^{2} = 385. 3^{2}\)

\(\left(\right. 1.3 \left.\right)^{2} + \left(\right. 2.3 \left.\right)^{2} + \left(\right. 3.3 \left.\right)^{2} + \ldots + \left(\right. 10.3 \left.\right)^{2} = 385. 3^{2}\)

Do đó \(A = 3^{2} + 6^{2} + 9^{2} + \ldots + 3 0^{2} = 3465\).

a) A=(2/7.1/4-1/3.2/7):(2/7.3/9-2/7.2/5)

A=[2/7(1/4-1/3)]:[2/7(1/3-2/5)]=(1/4-1/3):(1/3-2/5)=1 1/4

b) B=51​(72​+31​)−31​(72​+31​)43​(51​−72​−31​+72​)​=(51​−31​)(72​+31​)43​(51​−31​)​=15211​.

Bước làm:

Bước 1: Đưa số hữu tỉ về dạng phân số.

Bước 2: Đưa phép chia về dạng phép nhân các phân số.

Bước 3: Áp dụng tính chất của phép nhân các phân số: Bao gồm giao hoán, kết hợp, phân phối với phép cộng (trừ).

a) \(A = \frac{3}{5} . \&\text{nbsp}; \frac{6}{7} + \frac{3}{7} . \&\text{nbsp}; \frac{3}{5} - \frac{2}{7} . \&\text{nbsp}; \frac{3}{5}\)
\(= \frac{3}{5} \cdot \left(\right. \frac{6}{7} + \frac{3}{7} - \frac{2}{7} \left.\right) = \frac{3}{5}\)
b) \(\&\text{nbsp}; B = \left(\right. - 13 \cdot \frac{2}{5} + \frac{- 2}{9} \cdot \frac{2}{5} + \frac{2}{5} \cdot \frac{11}{9} \left.\right) \cdot \frac{5}{2}\)
\(= \left(\right. - 13 - \frac{2}{9} + \frac{11}{9} \left.\right) \cdot \frac{2}{5} \cdot \frac{5}{2} = - 13 + \left(\right. \frac{11}{9} - \frac{2}{9} \left.\right) = - 12.\)
c) \(C = \left(\right. \frac{- 4}{5} + \frac{5}{7} \left.\right) \cdot \frac{3}{2} + \left(\right. \frac{- 1}{5} + \frac{2}{7} \left.\right) \cdot \frac{3}{2} = \left(\right. \frac{- 4}{5} + \frac{5}{7} + \frac{- 1}{5} + \frac{2}{7} \left.\right) \cdot \frac{3}{2} = \left(\right. \left(\right. \frac{- 4}{5} + \frac{- 1}{5} \left.\right) + \left(\right. \frac{5}{7} + \frac{2}{7} \left.\right) \left.\right) \cdot \frac{3}{2} = 0.\)
d) \(D = \frac{4}{9} : \left(\right. \frac{1}{15} - \frac{10}{15} \left.\right) + \frac{4}{9} : \left(\right. \frac{2}{22} - \frac{5}{22} \left.\right)\)
\(= \frac{4}{9} : \frac{- 3}{5} + \frac{4}{9} : \frac{- 3}{22} = \frac{4}{9} \cdot \frac{- 5}{3} + \frac{4}{9} . \&\text{nbsp}; \frac{- 22}{3}\)
\(= \frac{4}{9} \cdot \left(\right. \frac{- 5}{3} + \frac{- 22}{3} \left.\right) = \frac{4}{9} . \&\text{nbsp}; \frac{- 27}{3} = - 4.\)

Today I will talk about topic 1 is : Talk about your hobbies. So let's go!

My favorite hobby is singing, dancing, play the violin and piano and I like doing that activities because that's my favorite hobby and my future job to so I like doing them. I usually do it in the afternoon and when I have freetime because my study schedule is quite busy, I usually do those things when I have free time.And you know why I like doing those activities?Because in 2031, when I am in 12th grade, I will take the entrance exam to the People's Public Security School of Culture and Arts.My speech ends here. Thank you for reading this article.

1. My full name is Doan Ngoc Hoang Nghi

2. My favorite hobby is singing, dancing. I usually do it

3. My favorite song is all Kpop and Vpop song. I like it because it makes me more happy

4. I reduce trash by doing lots of things I don't really remember and I think it's really important

5. My favorite subject is music, P.E and art