1 If my father didn't smoke too much, he wouldn'e have a bad cold

2 If she were tall enough, she could join the basketball team

3 If I had much time, I would visit my grandparents very often

4 If he knew her address, he could visit her

5 If the bike weren't too small, I could ride it

6 If they had enough money, they would buy the tickets for the concerts

7 If I had a car, I wouldn't have to get up early to catch the bus

8 If Mark were't talkative, people would like him 

9 If Ken played football well enough, he would be chosen to be in the school team

10 If Emma read book often, her essays wouldn't be bad

1,C

2,A

3,C

4,C

5.B

1,A

2,D

3,D

4,A

5,D

1,C

2,B

3,B

4,C

5,C

6,D

7,D

8,D

9,C

10,A

A

I

1C

2A

3C

4C

5B

II

1A

2D

3D

4A

5D

B

III

1C

2B

3B

4C

5D

6C

7A

8D

9C

10A

3 D

4 A

5 A

6 B

7 A

9 D

10 C

2 C

4 A

2 interesting 

Bài II, câu 3 chọn I 

4 - high

5 - ride

6 - put it on

7 - happy

9 - looking

10 - not to smoke

Bài III 

2 - C 

4 - A 

a) Xem hình vẽ.

b)

c) Điền vào chỗ trống:
1)  (vì là hai góc kề bù).
2)  (theo giả thiết và căn cứ vào 1).
3)  (căn cứ vào 2).
4)  (vì là hai góc đối đỉnh).
5)  (căn cứ vào 4 và giả thiết).
6)  (vì là hai góc đối đỉnh).
7)  (căn cứ vào 6 và 3).

d)Trình bày lại cách chứng minh một cách gọn hơn.
Ta có:  (hai góc kề bù) mà  (gt) 
nên .
Suy ra 
Lại có  (hai góc đối đỉnh).
Suy ra .

Bạn cần giải thích bài nào nhỉ?

2:

a: =(x-y)^2-4

=(x-y-2)(x-y+2)

b: =49-(16x^2-8xy+y^2)

=49-(4x-y)^2

=(7-4x+y)(7+4x-y)

3:

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

b: =(x+y-x+y)[(x+y)^2+(x-y)(x+y)+(x-y)^2]

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

=2y(3x^2+y^2)

\(45.\)

\(M=a^3+b^3+3ab\left(a^2+b^2\right)+6a^2b^2\left(a+b\right)\)

\(=\left(a+b\right)\left(a^2-ab+b^2\right)+3ab\left[\left(a^2+2ab+b^2\right)-2ab\right]+6a^2b^2\left(a+b\right)\)

\(=\left(a+b\right)\left(a^2-ab+b^2\right)+3ab\left[\left(a+b\right)^2-2ab\right]+6a^2b^2\left(a+b\right)\)

\(=a^2-ab+b^2+3ab\left(1-2ab\right)+6a^2b^2\)

\(=a^2-ab+b^2+3ab-6a^2b^2+6a^2b^2\)

\(=a^2+2ab+b^2\)

\(=\left(a+b\right)^2\)

\(=1^2\)

\(=1\).

42:

a^3+b^3+c^3-3abc

=(a+b)^3+c^3-3ab(a+b)-3bac

=(a+b+c)(a^2+2ab+b^2-ac-bc+c^2)-3ab(a+b+c)

=0

=>a^3+b^3+c^3=3abc

44:

a: x^3+y^3+3xy

=(x+y)^3-3xy(x+y)+3xy

=1^3-3xy+3xy=1

b: x^3-y^3-3xy

=(x-y)^3+3xy(x-y)-3xy

=1^3+3xy-3xy=1

Bài 39:

a. 

PT $\Leftrightarrow x^3-3^3+x(2^2-x^2)=1$
$\Leftrightarrow x^3-27+4x-x^3=1$

$\Leftrightarrow 4x-27=1$

$\Leftrightarrow 4x=28$

$\Leftrightarrow x=7$
b.

PT $\Leftrightarrow x^3+3x^2+3x+1-(x^3-3x^2+3x-1)-6(x^2-2x+1)=-10$
$\Leftrightarrow 6x^2+2-6x^2+12x-6=-10$

$\Leftrightarrow 12x-4=-10$

$\Leftrightarroq 12x=-6$

$\Leftrightarrow x=\frac{-1}{2}$