B

C

D

C

B

B

D

C

A

C

C

D

B

D

D

B

B

B

C

A

a) \(\left(x+3\right)\cdot\left(x^2-3x+9\right)\)

b) \(\left(x-\dfrac{1}{2}\right)\cdot\left(x^2+\dfrac{1}{2}x+\dfrac{1}{4}\right)\)

c) \(\left(2x+y\right)\cdot\left(4x^2-2xy+y^2\right)\)

C

\(5y\left(y-x\right)+15x\left(x-y\right)\)

= \(5y\left(y-x\right)-15x\left(-x+y\right)\)

= \(5y\left(y-x\right)-15x\left(y-x\right)\)

= \(\left(y-x\right)\cdot\left(5y-15x\right)\)

=\(\left(y-x\right)\cdot5\left(y-3x\right)\)

bài 1:

a) 3x-9xy

= 3x(1-3y)

b)\(18x^2y^2-9x^3y+36xy^2\) 

= \(9xy\left(2xy-x^2+4y\right)\)

c) \(5y\left(y-x\right)+15x\left(x-y\right)\)

= \(5y\left(y-x\right)-15x\left(y-x\right)\)

= \(\left(y-x\right)\cdot\left(5y-15x\right)\)

= \(\left(y-x\right)\cdot5\left(y-3x\right)\)

a(b+3)-b(3+b)

=(3+b)(a-b)

Thay số, có: (3+1997).(2003-1997)

= 2000.6 =12000

xy(x+y)-2x-2y

xy(x+y)- 2(x+y)

(x+y).(xy-2)

Thay số, co: 7. (8-2)

7.4=28

6 Could you tell me what the local people say?

7 I find it more interesting to see romantic films than to see war films

8 A lot of people travel from Oxford to London by train everyday

9 Why don't we ask the local people for help?

10 Does the La Chi's largest apartment have an ancestral altar?

a) Xét \(\Delta ADP\) = \(\Delta AHP\) có: ( cạnh huyền -cạnh góc vuông)

góc APD = APH=90o

AD = AH

AP chung                                               

=> AD=AH (1)

CMTT với \(\Delta AEQ=\Delta AHQ\left(CH-CGV\right)\)

=> AE= AH (2)

Từ 1 và 2 => AD= AE

=> A là trung điểm của DE

b) Xét \(\Delta DHE\) có:

DP=PH; HQ=QE

=> PQ là đg trung bình của tam giắc DHE

=> PQ// DE; PQ=1/2 DE

c) Xét tứ giác APHQ có: góc HPA= 90o; Góc A =90o; góc HQA=90o 

=> Tứ giác APHQ là HCN

=> PQ=AH ( theo t/c HCN)  

1 What a beautiful village!

2 When did you build this stilt house?

3. It's more convenient to live in a big city than to live in a village

4 Where is his address?

5 In spite of being quite poor, the villagers live a happy and heathy way.

\(Ca+HCl\) -> \(Ca_2CO_2+H_2\)