1; the second-hand car patrick bought was almost new ..................it was made in the 1990s

a or b although c because d however

2 were you able to find the person ..................wallet you fond ?

a who b which c whose d that

3 lan : let's go to vung tau on the weekend

tom :.......... a yes , please b yes , let's c that's a fine day d that's a good trip

4 i will give you another hour to ............................. up your mind a give b go c make d take

5 dick ..................in london when i last saw him

a is working b was working c has worked d has been working

6 i wish i ........................... a lot of money but i do not

a have earned b earn c earned d will earn

7 egypt is famous .......................ancient pyraminds

a on b for c from d to

8 designers have taken ..................................... from many things in life a inspiration b inspire c inspired d inspiring

9 dasy : that's an excellent drawing , hoa

hoa :....................................

a that's a good idea

b thank you

c well done

d i am sorry

10 that's a nice coat , and the colour .......................you well

a suits b matches c fits d agrees

11 linda : would you like some bread ?

miss hoa : ................................ i am rather hungry

a no , i would not

b yes , please

c yes , i like

d no , thanks

12 tan usually wears uniform ar school . at home , he wears .......................clothes a formal b national c occasional d casual 13 peter : can you come for dinner tonight

? john : ................................. i have a lot of things to do

a i agree b i'm afraid not c good idea d it's all right

14 this is the best movie ............................. i have seen a who b whom c where d that

3, 

A = n²+n+1 = n(n+1)+1

a, 

+ Nếu n chẵn

=> n(n+1) chẵn 

=> n(n+1) lẻ => ko chia hết cho 2

+ Nếu n lẻ

Mà 1 lẻ

=> n+1 chẵn

=> n(n+1) chẵn

=> n(n+1)+1 lẻ => ko chia hết cho 2

KL: A không chia hết cho 2 với mọi n thuộc N (Đpcm)

b, + Nếu n chia hết cho 5

=> n(n+1) chia hết cho 5

=> n(n+1)+1 chia 5 dư 1

+ Nếu n chia 5 dư 1

=> n+1 chia 5 dư 2

=> n(n+1) chia 5 dư 2

=> n(n+1)+1 chia 5 dư 3

+ Nếu n chia 5 dư 2

=> n+1 chia 5 dư 3

=> n(n+1) chia 5 dư 1

=> n(n+1)+1 chia 5 dư 2

+ Nếu n chia 5 dư 3

=> n+1 chia 5 dư 4

=> n(n+1) chia 5 dư 2

=> n(n+1)+1 chia 5 dư 3

+ Nếu n chia 5 dư 4

=> n+1 chia hết cho 5

=> n(n+1) chia hết cho 5

=> n(n+1)+1 chia 5 dư 1

KL: A không chia hết cho 5 với mọi n thuộc N (Đpcm)