1.If he had hurry,he hadn't missed the train.

2.It's the first time i have ever seen that men.

3.The furniture was too expensive for me to buy.

4.He was taught to drive when he was eighteen.

5.He was unhappier than he had been before.

6.Bill doubted whether John would become.

7.Do you happen to have change for a pound.

8.He didn't win the race.

9."How do you like my new dress" she asked John.

10.There is a train leaves at 8 o'clock every morning.

11.It can't be denied that she has a beautiful voice.

12.Do you mind helping me to put the chairs away.

13.You've to see the manager tomorrow morning.

14.Every time we rang,there was no answer.

15.Which one do you want,the blue or the green.

16.She thought Rome was even worse than Paris.

17.So long as you arrive before eleven,i can meet you.

18.All prisoners will be caught again by tonight.

19.I've warned you about your going near that dog.

20.I'd rather you didn't tell him.

21.You'll need an up-to-dated visa for Andora.

22.The office manager wondered why he hadn't got a computer

23.John advised Elizabeth not to lend him any more money.

a) = (9x²)² +2² = (9x²)² + 2×9x²×2 + 2² - 36x² = (9x²+2)² -(6x)² = (9x²+2+6x)(9x²+2-6x)

b) = x⁴ - 16x² + 64+36= x⁴-16x²+100=x⁴+20x²+100-36x²= (x²+10)² - (6x)²= (x²-6x+10)(x²-6x+10)

d) Đặt a=x²+x,ta có: a²+4a-12 = a²-2a+6a-12= a(a-2)+6(a-2) = (a+6)(a-2) tương đương (x²+x+6)(x²+x-2)=(x²+x+6)(x-1)(x+2)

e)Đặt a=x²+x+1(a>0), ta có: a(a+1)-12= a²+a-12= a² -3a+4a -12= a(a-3) +4(a-3)=(a+4)(a-3) tương đương (x²+x+1+4)(x²+x+1-3) =( x² +x+4)(x²+x-2)=(x²+x+4)(x-1)(x+2)