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Câu 28: chọn đáp án A

1. Sarah finds her mobile phone very useful. She uses it all the time.
2. Vicky doesn't know where her watch is. She has lost it.
3. We're in the middle of decorating our kitchen, so we can't cook any meals. We're getting them from a take-away restaurant this week.
4. Claire is on a skiing holiday. She is enjoying it, she says on her postcard.
5. The colour of this paint is absolutely awful. I hate it.
6. These figures certainly should add up. I have checked them several times already.
7. Trevor and Laura like Scrabble. They play it most evenings.
8. These flowers are dying. You haven't watered them for ages.

1. The children's bedroom is big.
2. Their cousins' skateboards are new.
3. My close friend's scarf is very nice.

C: 9 nghiệm thực nhé!

đề ??

đề ??

24A

25D

26 Giá trị lớn nhất của hàm số là: \(√34 - 4√2\)

27 C

4) 

` -x ( x- y)^2 = -x ( x^2 - 2xy + y^2) = -x^3 + 2x^2y - xy^2 `

` ( x - y)^3 = x^3 - 3x^2y + 3xy^2 - y^3 `

` y^2 ( y - 2x ) = y^3 - 2xy^2 `

` - x^3 + 2x^2y - xy^2 + x^3 - 3x^2y + 3xy^2 - y^3 + y^3 - 2xy^2 `

` = -x^3 + x^3 + 2x^2y - 3x^2y - xy^2 + 3xy^2 - 2xy^2 - y^3 + y^3 = -x^2y `

2) 

` ( -x - 2y)^3 = - ( x + 2y)^3 = - [ x^3 + 6x^2y + 12xy^2 + 8y^3] `

` = - x^3 - 6 x^2 y - 12xy^2 - 8y^3 `

` => 2 ( -x -2y)^3 = -2x^3 - 12x^2y - 24xy^2 - 16y^3 `

` = x( 2y - x ) ( x+2y) = x [(2y - x) ( x+2y)] `

` = x ( 2y^2 - x^2 ) = 2xy^2 - x^3 `

` = -2x^3 - 12x^2y - 24xy^2 - 16y^3 + 2xy^2 - x^3 `

` = - 3x^3 - 12x^2y - 22xy^2 - 16y^3 `