a) \(P=\dfrac{1}{2-\sqrt{3}}+\dfrac{1}{2+\sqrt{3}}\)

\(=\dfrac{2+\sqrt{3}}{\left(2-\sqrt{3}\right)\left(2+\sqrt{3}\right)}+\dfrac{2-\sqrt{3}}{\left(2-\sqrt{3}\right)\left(2+\sqrt{3}\right)}\)

\(=\dfrac{2+\sqrt{3}+2-\sqrt{3}}{\left(2-\sqrt{3}\right)\left(2+\sqrt{3}\right)}\)

\(=\dfrac{4}{4-3}\)

\(=4\)

b) \(Q=\left(1+\dfrac{\sqrt{x}+2}{\sqrt{x}-2}\right).\dfrac{1}{\sqrt{x}}vớix>0,x\ne4\)

\(=\left(\dfrac{\sqrt{x}-2+\sqrt{x}+2}{\sqrt{x}-2}\right).\dfrac{1}{\sqrt{x}}\)

\(=\)\(\dfrac{2\sqrt{x}}{\sqrt{x}-2}.\dfrac{1}{\sqrt{x}}\)

\(=\dfrac{2\sqrt{x}}{\sqrt{x}\left(\sqrt{x}-2\right)}\)

\(=\dfrac{2}{\sqrt{x}-2}\)

31. did / What/ do/ people/ when/ there./ you/the/ were?

A.What did the people do when you were there?

B. What did people do when the you were there?

C. When did the people do what you were there?

D. What people do the what you were there?

26. A. was B. were C. is D. are 

27. A. go B. going C. went D. goes  

28. A. has B. have C. had D. having 

29. A. an B. a C. any D. some

30. A. wear B. wore C. wearing D. to wear 

We are planting these trees now

=> Trees are being planted in the garden by them. 

1.     Ann carried heavy furniture when she helped her friend move. Her back hurts now.

=> Ann’s back wouldn’t hurt now if she had not carried heavy furniture when she helped her friend move

2.     Paulo is working on two jobs right now, so he doesn't have time to help you with your remodelling.

=>  If Paulo didn't work on two jobs, he would have time to help you with your remodeling

3.     I wasn't working at the restaurant last night. I didn't wait at your table.

=> If I had been working at the restaurant last night, I would have worked at your table

4.     Because Diane asked questions every time she didn't understand a problem, she has a good understanding of geometry now.

=>  If Danie hadn't asked questions everytime she didn't understand a problem, she would have a good understand of geometry now 

1 It's David's cat. It's his

2 it's Linda's watch . It's hers

3 It's your car .It's yours

4 It's the boys ' ball .It's theirs

5 It's your game . It's yours

6 It's my bike . It's mine

a) 40x²y - 8xy - 16x²y²

= 8xy( 5x - 1 - 2xy)

b) (x-y)(x+y)-3(x-y)    

= (x - y)( x + y - 3)

c)(x-y)² -5(x-y)

=(x - y)(x - y - 5)

1 m³=1 cc

1m=10 dm

1cm=10 mm

1tấn=1000 kg

1m³=1000dm³

C. Từ 1 đến 3 tháng