a) Ta có: ( x - 2 )( x + 2 ) = ( x )² - 2² = x² - 4.

b) Ta có: 56.64 = ( 60 - 4 )( 60 + 4 ) = 60² - 4² = 3600 - 16 = 3584.

a) Ta có: ( x2 -1 )( x2 + 2x )

= x2( x2 + 2x ) - ( x2 + 2x )

= x4 + 2x3 - x2 - 2x

b) Ta có ( x + 3 )( x2 + 3x -5 )

= x( x2 + 3x -5 ) + 3( x2 + 3x -5 )

= x3 + 3x2 - 5x + 3x2 + 9x - 15

= x3 + 6x2 + 4x - 15

c) Ta có ( x -2y )( x2y2 - xy + 2y )

= x( x2y2 - xy + 2y ) - 2y( x2y2 - xy + 2y )

= x3y2 - x2y + 2xy - 2x2y3 + 2xy2 - 4y2

d) Ta có ( 1/2xy -1 )( x3 -2x -6 )

= 1/2xy( x3 -2x -6 ) - ( x3 -2x -6 )

= 1/2x4y - x2y - 3xy - x3 + 2x + 6

1. A

2. C

3. B

4. C

5. C

1. ______ people are there in your family?

A. How long

B. How far

C. How much

D. How many

2. _______ is that? - My brother.

A. Which

B. Who

C. What

D. When

3. Which word contains a different sound from the others?

A. lamp

B. fan

C. bag

D. father

4. ______ does your mother do? - She’s an engineer.

A. Where

B. Who

C. What

D. Which

5. How _____ is your little brother? - He’s three years old?

A. many

B. much

C. years

D. old

1 – e

2 – d

3 – b

4 – a

5 – c 

1. A

2. B

3. B

4. A

5. A

1. A

2. B

3. B

4. A

5. A