o ò ó o nhau 

Đặt 111...1(n chu so 1)=x ->10ⁿ=9x+1

Ta có:

a= 11....1(2n chu so 1)=x.10ⁿ+x=x(9x+1)+x=9x²+x+x

b=11...11(n+1chu so 1)=x.10+1

c=66...6(n chu so 1)=6x

-> a+b+c+8=9x²+x+x+10x+1+6x+8

                 =9x²+18x+9

                 = (3x)²+2.3.3x+3²=(3x+3)(3x+3)=(3x+3)²=(3.11..1+3)²=33..36²

->ĐPCM

vi em ay không thích uống nước

x\(\times\)(5+2+3)=100

x\(\times\)10=100

x=100\(\div\)10=10

Vậy x =10

= 45 cm²

Duyệt nhé

Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) OPPOSITE in meaning to the underlined word(s) in each of the following questions.

When you consider all the advantages you've gained I think you'll admit you had a good run for your money

A. a lot of loss from your money

B. a lot of benefits from your money

C. a lot of advantages from your money

D. a lot of failures in making your money

Cho tam giác ABC có AB=AC. Trên cạnh AB và AC lần lượt lấy hai điểm M và N sao cho AM=AN. Nối BN và CM gặp nhau tại O.

a)  B A C ^  là góc chung của các tam giác nào?

b) BC là cạnh chung của các tam giác nào?

c) Các cặp góc nào kề bù nhau

d) Tìm các tam giác có cạnh là AO

1. i'm glad to know that you are going......on...........a picnic

2. at the moment, most of the town is being covered .......with.....................snow

3. in this company, everybody is responsible ................ turning off the lights before leaving

4. the boy fell........................the water and was drowned

5. he suffered......................................constant sleepiness

6. they have been absent ........from.............. school very often lately

7. is she capable................ using computers ?

8. they have made use............................. the house after remodeling it

9. they started .....at.......... home because andy wasn't keen .........on............. going out in the rain

10. i wrote the letter to complain ......about............... the good i brough in the shop

Tìm và sửa lỗi trong mỗi câu:

1. Water is boiling at 100 degrees Celcius => is boiling = boils ( hiện tại đơn - sự thật hiển nhiên)

2. Alexander Bell taught in a school for deaf

3. When he heard the words, Watson rushed upstairs, run into Bell's room, and shouted, ''I heard you!'