xét: ab + ba = 10a + b + 10b + a = ( 10a+ a ) + ( 10b + b ) 

= 11a + 11 b = 11.( a + b ) chia hết cho 11

vậy: ab + ba chia hết cho 11 ( đpcm )  

tìm x

giam 4%

what's your name ?

💯 TEST ENGLISH 6 💯

(Bài Tập Nâng Cao Dành Cho Những Bạn Chuyên Môn TA)

1. It's a good idea to see your doctor regularly for________

A. a revision

B. a control

C. an investigation

D. a check-up

2. Last year the potato harvest was very disappointing, but this year it looks as though we shall have a better_________

A. product

B. outcome

C. amount

D. crop

3. When the starter gave the______ all the competitors in the race began to run round the track

A. signal

B. warning

C. shot

D. show

4________from Bill, all the students said they would go

A. except

B. only

C. apart

D. separate

5 The new manager explained to the staff that she hope to________new procedures to save time and money

A. manufacture

B. establish

C. control

D. restore

Nguồn: Mai_Chill 🖤