Mai Vương Minh's Profile

a) 3x^3 - x^2 - 21x + 7

= x^2(3x - 1) -7(3x - 1)

= (x^2 - 7)(3x - 1)

b) x^3 - 4x^2 - 8x + 8

= (x + 2)(x^2 - 2x + 4) - 4x(x + 2)

= (x + 2)(x^2 - 2x + 4 - 4x)

= (x + 2)(x^2 - 6x + 4)

c) x^3 - 5x^2 - 5x + 1

= (x + 1)(x^2 - x + 1) - 5x(x + 1)

= (x + 1)(x^2 - x + 1 - 5x)

= (x + 1)(x^2  - 6x + 1)

P=x^2-4x+5

P=(x-2)^2+1

Ta có: (x-2)^2 > 0 (với mọi x)

         =>GTNN của P là 1 khi (x-2)^2=0

                                         =>x-2=0

                                         =>x=2

x^2 +8x -20

=x^2+10x-2x-20

=x(x-2)+10(x-2)

=(x+10)(x-2)

1.They didn't let me go 

2. When John was four, he came to London with his parents

3.How long are you lived there?

4.They are go to the school on foot

5.Do you mind if i smoke in the room?

6.His garden isn't as large as mine

7.We haven't talked to your sister for the long time

8, There're more than 80 stores in the mall

9. The toys krpt in the box are worth 30 dollars

10. This school different from mine

_______________________________________________________________________________________

She is at the age of sixteen

1/different

2/ useful 

3/toothache

4/healthy

5/healthy

6/appointment

7/friendly

8/healthy

9/beautiful

10/carefully

11/useful

12/beautiful

Yes, it is

1/How often do you clean your teeth a day?

2/Who is always doing the homework?

3/When does Ben misses the bus?

10^30>2^100

Bài giải 

Đổi: 10dm=100cm

Số dây thép bố Nam cắt thành 6 đoạn bằng nhau là:

100-10=90(cm)

Mỗi đoạn dây bố Nam cắt ra dài số cm là :

90:6=15(Cm)

Đáp số: 15cm