9 + 87 = 21

Ex: Complete the following letter, using the suggestive words

Dear Sir,

1. I/be/interest/learning/English.

=> I am interested in learning English.

2.I/like/information/your school.

=> I would like some information about your school.

3.I/speak/English/but/I want/improve/reading/writing.

=> I can speak English but I want to improve my reading and writing.

4.you/please/send/details/the course/fees?

=> Could you please send details of courses and fees ?

5.I/look/forward/hearing/you soon.

=> I am looking forward to hearing you soon.

He can be found at home every time we want

1000+1400-400-500=1500

4x⁴+1

=(2x²)²+4x²+1-4x²

=(2x²+1)²-(2x)²

=(2x²+2x+1)(2x²-2x+1)

1. Amanda has made great progress this term.

2. He objects to anyone touching his records.

3. The less huried my boss is, the worse he works.

dễ như ăn cháo

Vì ab chia hết cho 9 nên (8 +7 +a +b) phải chia hết cho 9 
Vì a,b =<9 => a+b =3 hoặc a+b =12 
Với a +b =3 => (a=1,b=2) ;(a=0,b=3);(a=2,b=1);(a=3;b=0) 
Với a +b=12 =>(a=4,b=8);(a=5,b=7);(a=6,b=6);(a=7,b=5... 
=> có 11 các giá trị của ab thỏa mãn