Một hợp chất gồm nguyên tố R có hóa trị x ( trong đó hóa trị 1 ≤ x ≤ hóa trị 3 ) và nguyên tố oxi. Biết rằng phân tử hợp chất này nặng gấp 2.55 lần nguyên tử canxi.

a) Viết công thức dạng chung của hợp chất gồm R ( hóa trị x ) và nguyên tố oxi.

b) Xác định tên và ký hiệu của nguyên tố R.

Phân tích thành nhân tử:

a) \(x^4-x^2-2x-1\)

b) \(x^2+25+10x-y^2-2y-1\)

c) \(x^2+4y^2-4xy-z^2+6z-9\)

d) \(x^2-3z\left(3z-2\right)-12xy-1+36y^2\)

e) \(4a^2b^2-\left(a^2+b^2-c^2\right)\)

f) \(x^3+3x^2-9x-27\)

g) \(x^{m+4}+x^{m+3}-x-1\)

Phân tích thành nhân tử:

a) \(\left(3x-1\right)^2-\left(5x+3\right)^2\)

b) \(\left(2x-y+4z\right)^2-\left(x+y-z\right)^2\)

c) \(\left(x^2+xy\right)^2-\left(x^2-xy-2y^2\right)\)

d) \(x^4-x^2-2x-1\)

e) \(x^2+25+10x-y^2-2y-1\)

f) \(x^2+4y-4xy-z^2+6z-9\)

g) \(x^2-3z\left(3z-2\right)-12xy-1+36y^2\)

h) \(4a^2b^2-\left(a^2+b^2-c^2\right)\)

l) \(x^3+3x^2-9x-27\)

i) \(x^{m+4}+x^{m+3}-x-1\)

43. “You must decide what you want to do. “ He said to his daughter.

- He urged....................................................................................................................................

44.”It’s a very nice evening. Why don’t we go for a walk ?” Jim suggested.

- Jim said that .......................................................... and suggested ..........................................

45.”Do as I tell you. You are a naughty boy.” Mrs Brown said.

- Mrs Brown told ..............................................and complained that .....................................

46.”I wonder who is coming on the excursion tomorrow. I hope it won’t rain.”She said

- She wondered .......................................................................and .........................................

47.”Don’t you know how to behave in lessons ?” The techer told his students.

- The teacher asked ...................................................................................................................

48.I asked the policeman, “Do you know how far is it to the station ?”

- I asked ...................................................................................................................................

49.” I shall expect to see you next Wednewday, Mary” Peter said

- Peter said to Mary that ...........................................................................................................

50.‘Do as I tell you or you’ll be punished. I’ll teach you who is master in this house” He said

He asked me.......................................................................................... ...............and said that ................................................................................................................................................

51.”Do you have any shampoo, Alice? I must wash my hair.” Dick said.

Johny said that ..................................................................................................... and asked .................................................................................................................................................

52.”When we finish this game, we’ll have dinner.” My children said to me.

- My children told me that .......................................................................................................

53.”Let’s go to the zoo.” They said to me.

- They asked ....................................................../ They suggested .........................................

54.”Do you like it ? ” -Yes

- He asked me ........................................................ and I said that ..........................................

55.”Do you phone your parents often, Hoa ?” Nam said

- Nam asked ..............................................................................................................................

56.”Must you go now, Miss White ? ” Mr Brown said

- Mr Brown asked ................................................................................................................

57.”Be modest if you are a good student.” My father said

- My father told me ..............................................................................................................

58.”Who put salt in my coffee ?” he said.

- He asked her ....................................................................................................................

59.”What time do you often go to bed, Mr Leath ? “ The policeman said.

- The policeman asked ......................................................................................................

60.He said to me “ Listen ! Can you hear someone coming ?”

- He told .................................... and asked .....................................................................