a: \(x^2-9y^2=\left(x-3y\right)\left(x+3y\right)\)

c: \(\left(x+5\right)^2-16=\left(x+1\right)\left(x+9\right)\)

e: \(\left(2x+3\right)^2-\left(x-7\right)^2\)

\(=\left(2x+3+x-7\right)\left(2x+3-x+7\right)\)

\(=\left(3x-4\right)\left(x+10\right)\)

b)\(\sqrt{x^2-10x+25}=2x-3\)                                               ĐK:x≥3/2

\(\Leftrightarrow\sqrt{\left(x-5\right)^2}=2x-3\)

\(\Leftrightarrow\left|x-5\right|=2x-3\)

\(\Leftrightarrow\left[{}\begin{matrix}x-5=2x-3\\x-5=3-2x\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=\dfrac{8}{3}\end{matrix}\right.\)

Vậy phương trình có 2 nghiệm là ... 

a: Ta có: \(\sqrt{25x+75}+3\sqrt{x-2}=2+4\sqrt{x+3}+\sqrt{9x-18}\)

\(\Leftrightarrow5\sqrt{x+3}-4\sqrt{x+3}=2\)

\(\Leftrightarrow x+3=4\)

hay x=1

c)ĐK:x≥1/2

\(\sqrt{x+\sqrt{2x-1}}+\sqrt{x-\sqrt{2x-1}}=\sqrt{2}\)

\(\Leftrightarrow\sqrt{2x-1+2\sqrt{2x-1}+1}+\sqrt{2x-1-\sqrt{2x-1}+1}=2\)

\(\Leftrightarrow\sqrt{\left(\sqrt{2x-1}+1\right)^2}+\sqrt{\left(\sqrt{2x-1}-1\right)^2}=2\)

\(\Leftrightarrow\left|\sqrt{2x-1}+1\right|+\left|\sqrt{2x-1}-1\right|=2\)

\(\Leftrightarrow\sqrt{2x-1}+1+\left|\sqrt{2x-1}-1\right|=2\)  (do \(\sqrt{2x-1}+1\ge0\))

\(\Leftrightarrow\sqrt{2x-1}+1+\left|1-\sqrt{2x-1}\right|=2\)

Ta có:\(\sqrt{2x-1}+1+\left|1-\sqrt{2x-1}\right|\ge\sqrt{2x-1}+1+1-\sqrt{2x-1}=2\)

Dấu "=" xảy ra \(\Leftrightarrow\left(\sqrt{2x-1}+1\right)\left(1-\sqrt{2x-1}\right)\ge0\)

                        \(\Leftrightarrow\dfrac{1}{2}\le x\le1\)

Vậy phương trình có tâp nghiệm \(S=\left\{x|\text{​​}\dfrac{1}{2}\le x\le1\right\}\)

Part 4: QUESTIONS 16-23: Read the information about Schnauzer dogs. Choose the best word (A, B or C) for each space (16-23). For questions 16-23, mark A, B or C on the answer sheet.

                                                                                   Schnauzer Dogs 

There are three sizes (0) ………… Schnauzer dog. The two smaller sizes first (16)………….. to England over 50 years ago, but the Giant Schnauzer has not (17)…………. here very long. The name Giant is a good one because the dogs are 65 to 67.5 cm high. All the dogs (18)…………. long hair, which shoukd be cut quite often. Most smaller Schnauzers (19)…………… grey in colour, (20)………….. the Giant Schnauzer is usually black. Schnauzers come from Germany, where farmers use the dogs to help (21)…………… with their sheep, and they are also used (22)………….. the police, because Schnauzer dogs are very intelligent. A Schnauzer makes (23)…………… nice family dog. It is friendly and very good with young children.

0.                 A. with                      B. of                  C. in

16.               A. came                    B. come            C. comes

17.               A. being                    B. be                 C. been

18.               A. has                       B. have             C. had

19.               A. were                     B. is                  C. are

20.               A. or                          B. if                  C. but

21.               A. them                     B. him              C. us

22.               A. from                      B. by                C. to

23.               A. the                         B. a                  C. any

PART 5 : QUESTIONS 24-33: Complete this letter. Write ONE word for each space (24-33). For questions 24-33, write your words on the answer sheet.

28 Long Road Brighton 22nd March

Dear Pat,

I arrived (Example : here) three weeks ago. I’m studying at a language school (24) in Brighton. The students come (25) from many diffirent countries and I (26) have made a lot of new friends. There (27) are classes for five hours every day. I (28) my teacher very much. (29)His name is John and he helps me (30) when I make mistake. I want (31) to visit London next weekend because I (32) am going Bck to my country on Monday. Can I see you there ? Please write to (33) me soon. With best wishes from Maria.

0B 

16A

17C

18B

19C

20C

21A

22B

23B

con xong toan roi a

Câu trả lời của AN là sai bởi vì 21/56 rút gọn thành 3/8 và 3/8 viết được dưới dạng số thập phân hữu hạn bởi vì

8 khi phân tích ra thành thừa số nguyên tố chỉ chứa số 2, đồng nghĩa không chứa số nào khác 2 và 5

=>21/56 viết được dưới dạng số thập phân hữu hạn

11)11) 3x(x-5)²-(x+2)³+2(x-1)³-(2x+1)(4x²-2x+1)=3x(x²-10x+25)-(x³+6x²+12x+8)+2(x³-3x²+3x-1)-(8x³+1)=3x³-30x²+75x-x³-6x²-12x-8+2x³-6x²+6x-2-8x³-1=-4x³-42x²+63x-11

nhìn khó thế

41.C

42.A

43.C

44.D

45.B

41C

42A

43C

44D

45B

C,A,C,DB