Cho biểu thức:

A = \(\left(\dfrac{1}{\sqrt{x-1}}+\dfrac{1}{\sqrt{x+1}}\right)^2.\dfrac{x^2-1}{2}-\sqrt{1-x}\)

a: Tìm dkxd

b: Rút gọn

c: Giải phương trình theo x khi A = 2

1) 120 + 20 : 4 - 2².3

=> 120 + 5 - 12

=> 125-12

=>113

2) ( 120 + 20 ) : 4 -

3) 120 + ( 20 : 4 - ).3

=> 120 + 1 . 3

=> 120 + 3

=> 123

b. x² - 7x = 4 - 7(x-3)

=> x² - 7x = 4 - 7x +21

=> x² - 7x + 7x = 25

=> x² = 25

=> \(\left[{}\begin{matrix}x=5\\x=-5\end{matrix}\right.\)

c.

1. is / how / weather / the / today / ?

=> __How is the weather today ?_______________________

2. play / can / the / you / piano / ?

=> __________Can you play the piano ?_______________

3. in / the dogs / are / front / my house / of .

=> _________The dogs are in front of my house________________

4. pencils / those / and / are / rulers.

=> __________Those are pencils and rulers._______________

5. bookshelf / reach / I / not / can / the .

=> ______I cannot reach the bookshelf___________________

6. tall / is / sister / and / my / pretty.

=> My sister is tall and pretty

a) ( x² - 4 ) . ( x² - 9 ) = 0

=> \(\left[{}\begin{matrix}x^2-4=0\\x^2-9=0\end{matrix}\right.=>\left[{}\begin{matrix}x^2=4\\x^2=9\end{matrix}\right.\)

= > \(\left[{}\begin{matrix}x=-2\\x=2\\x=3\\x=-3\end{matrix}\right.\)

- Ta có: ( 5x + 1 ) ² \(=\dfrac{36}{49}\)

=> \(\left[{}\begin{matrix}5x+1=\dfrac{6}{7}\\5x+1=-\left(\dfrac{6}{7}\right)\end{matrix}\right.\)

=> \(\left[{}\begin{matrix}5x=-\left(\dfrac{1}{7}\right)\\5x=-\left(\dfrac{13}{7}\right)\end{matrix}\right.\)

=> \(\left[{}\begin{matrix}x=-\left(\dfrac{1}{35}\right)\\x=-\left(\dfrac{13}{35}\right)\end{matrix}\right.\)

1. Lan's teacher wants her(spend) ....to spend............... more time on Math.

2. I promise I (try) .....will try............... my best next semester.

3. Linh needs (improve) ......to improve.................... her English writing.

4. They didn't try (learn) .....to learn............. all new words they (come) .......came.......... across.

5. You should (underline) ....underline............the words you want (learn) ..to learn......... .

6. Can you help me (move) ..........move....................... this table?

7. Minh always (get) ..GETS.... grade A for Physics, but last semester he (get) ...got..... B. So Minh's teacher asked him (study) .....to study................... harder this semester.

8. They were proud of (be) .......being........... so successful.

1. Lisa (not go) ....DIDN'T GO............to work yesterday. She wasn't feeling well.

2. It (not rain) .......DOESN'T RAIN...............very much in summer.

3. Most people (learn) ...LEARNT.............to swim when they are child.

4. Listen to those people. What language they (talk) ......ARE TALKING....................... ?

5. The moon (go) ..GOES....... round the earth in about 27 days.

6. That bag looks heavy. CAN I (help) .HELP............. you with it?

7. It's her birthday. She (have) .....IS HAVING.................. a mealk with her friends.

8. The letter (come) ......CAME.................. a few days ago.

- Giải phương trình

(1): ( x + 3 )⁴ +( x-1 )⁴ = 626

(2): ( 2x - 1 ) ³ + (x - 1 )³ + ( 2 - 3x )³ = 0

( 3 ) : 2x⁴ - 13x³ +24x² -13x +2 = 0