chạy , dận , về

1. He didn't go to the party because he was busy.

=> He was busy, so he didn't go to the party.

2. It's a pity. We can't speak English well.

=> We wish we could speak English well but it's a pity.

4. The man is my new boss. He is talking to the lady over there.

=> The man is talking to the lady over there, he is my new boss.

6. What a pity wife can't speak English.

=> I wish my wife can speak English.

7. The man called the police. His wallet was stolen.

=> The man wallet was stolen so his called the police.

8. English people speak very quickly. That's why I can't understand them.

=> If English people speaks slowly, I can understand them.

9. The last time we saw Peter was on Sunday.

=> We haven't seen Peter since on sunday.

10. This city had old buildings, but none can be found nowadays.

=> There used to have old buildings, but none can be found nowadays.

I don’t read  (not read) books

21.____have__you_received____any letter from your parents yet?(receive)
22.My brother ___has joined_____the army when he __was___young.(join/be)
23.Miss.Lee often__writes___when she was on holiday.(write)
24.He__leaved__home two weeks ago and we__have heard__from him since then.(leave/not hear)
25.Columbus___discovered___America more than 400 years ago.(discover)
26.We___have not seen ___them for a long time.(not see)
27.How long___have__you_studied____in this school?(study)
28.We__have not received__any letter from him since he_leaved____four months ago.(not receive/leave)
29.Mr.Pike__has lived___here since last month.(live)
31.How long__have______you__waied___for me?just a few minutes.(wai)
32.Mr.Jackson__painted____his house since last month.(paint)
34.The last train_leaved__the station at 5p.m.(leave)
36.We__have lived__here for over twenty years.(live)
37.He_has lived____in London for two years and then__has gone____ to Edinburgh.(live/go)
38.My brother_has written____several plays so far.He_has just finished_his second tragedy.(write/just/finish)
40.Tom has_ not bought___a new computer yet.(not buy)
41.I__have played__ football very often when I _was__younger.(play/be)
42.Tom_has seen__Christ since 1908.(see)
43.He__losed__his job last month and since then he__has been__out of work.(lose/be)
44.Mike_did not go___to the cinema with us last Saturday.(not go)
45.We__have not met___Mark since he __leaved__the town five years ago.(not meet/leave)
46.I_have never heard__that film.(never/hear)
48.It’s the first time she___has not ridden__a horse.(ride)
50.I_met___my aunt two years ago.(meet)
51.____have__you___met___Jane recently?(meet)
52.She_has played____ a lot of tennis since she___got___her new tennis racket.(play/get)
53.He_has already packed_his suitcase.(already/pack)
54.__has__your father__ever flown___a plane before?(ever/fly)
55._did____Mary_go____to Nha Trang last holiday?(go)

C1:

835× (3 + 6 ) = 835 × 9 = 7515

C2: 

Ta có :   3.5.7.17 chia hết cho 5 

              10 mũ 50 =  (2.5)mũ 50 = 2 mũ 50 . 5 mũ 50   chia hết cho 5

=> N = 3.5.7.17 + 10⁵⁰ chia hết cho 5.

a,  2x^2 - 5x + 3 = 0                                                                    b,    4x^2 - 5x +1 = 0

<=>2x^2 - ( 2x+ 3x ) + 3 = 0                                                        <=> 4x^2 - ( 4x + x ) + 1 = 0 

<=> 2x^2 - 2x - 3x +3 = 0                                                            <=> 4x^2 -  4x - x  + 1 = 0 

<=> 2x ( x - 1 ) - 3( x - 1 ) =0                                                      <=> 4x ( x - 1 ) - ( x - 1 ) = 0

<=> ( 2x - 3 ) ( x - 1) = 0                                                              <=> ( x - 1 ) ( 4x - 1 )  = 0

<=>  2x - 3 = 0  hoặc  x - 1 = 0                                                     <=>  x - 1 = 0  hoặc  4x - 1 = 0

<=>     x = 3/2       hoặc   x = 1                                                      <=>  x = 1       hoặc    x = 1/4