(2x²+x-6)+3(2x²+x-3)-9=0 

\(\Leftrightarrow\) 2x² + x - 6 + 6x² + 3x - 9 - 9 = 0 

\(\Leftrightarrow\)2x²  + 6x² + 3x + x = 6 + 9 + 9

\(\Leftrightarrow\)8x² + 4x = 24

\(\Leftrightarrow\)8x² + 4x - 24 = 0

\(\Leftrightarrow\)(x+2)(8x-12) = 0

\(\Leftrightarrow\)x + 2 = 0 hoặc 8x - 12 = 0

1) x + 2 = 0 \(\Leftrightarrow\)x = -2

2)8x - 12 = 0 \(\Leftrightarrow\)8x = 12 \(\Leftrightarrow\)x = \(\frac{12}{8}\)

Vậy Tập nghiệm của phương trình đã cho là S ={ -2 ; \(\frac{12}{8}\)}

Gọi r(x) = ax + b là dư trong phép chia f(x) cho ( x² - 1 )

Theo đề bài ta có :

f(x) = A(x).(x+1) + 2 

f(x) = B(x).(x-1) + 4 

f(x) = C(x).(x - 1)(x + 1) + ax + b 

[ A(x) , B(x) , C(x) là thương ]

Với x = -1 => \(\hept{\begin{cases}f\left(-1\right)=2\\f\left(-1\right)=-a+b\end{cases}}\Rightarrow-a+b=2\left(1\right)\)

Với x = 1 => \(\hept{\begin{cases}f\left(1\right)=4\\f\left(1\right)=a+b\end{cases}}\Rightarrow a+b=4\left(2\right)\)

Từ (1) và (2) => Ta có hệ phương trình \(\hept{\begin{cases}-a+b=2\\a+b=4\end{cases}}\)

Giải hệ ta được a = 1 , b = 3

=> f(x) chia (x²-1) dư x + 3

- Good luck !

Revision English 8

I. Find the word that has the underlined part pronounced differently from the others

1. A. laughed B. washed C. danced D. played

2. A. beds B. dogs C. porters D. books

3. A. pictures B. watches C. buses D. brushes

4. A. homework B. mother C. open D. judo

II. Circle the letter A, B, C or D before the best answer

5. My dad doesn’t mind my mom from work every day.

A. pick up B. picked up C. picking up D. picks up

6. Using computers too much may have harmful effects your minds and bodies.

A. on B. to C. with D. onto

7. I love the people in my village. They are so and hospitable.

A. friendly B. vast C. slow D. inconvenient

8. Among the , the Tay people have the largest population.

A. groups B. majorities C. ethnic minorities D. ethnic cultures.

9. People in the countryside live than those in the city.

A. happy B. more happily C. happily D. less happy

10. Viet Nam is mulultural country with 54 ethnic groups.

A. a B. an C. the D. A and C

11. We to the countryside two months ago.

A. go B. have gone C. went D. will go

12. What will you do if you the final examinations?

A. will pass B. would pass C. pass D. passed

13. It rained hard. , my father went to work. A. Therefore B. However C. Because D. So

14. She told me ………… her.

A. phone B. phoning C. to phone D. phones

15. We anything from James since we left school.

A. haven’t heard B. heard C. don’t hear D. didn’t hear

III. Supply the correct form of the words in brackets..

16. I am enough to have a lot of friends. (LUCK)   

=> Lucky

17. They enjoy the summer evenings in the countryside. (PEACE)

=> Peaceful

18. Those cats look . (LOVE)

=> lovely

19. It was of him to offer to pay for us both. (GENEROUSITY)

=> generous

20. Role-play is in developing communication skills. (HELP)

=> helpful

IV;Underline a mistake and correct

21.Their life has been more comfortably since they moved to the city.

=> comfortable

22.She looks more pretty in this white dress.

=> prettier

23.The manager wants us to work more hardly

=> harder

\(\frac{x-145}{855}+\frac{x-147}{853}=\frac{x-855}{145}+\frac{x-853}{147}\)

\(\Leftrightarrow\frac{x-145}{855}-1+\frac{x-147}{853}-1=\frac{x-855}{145}-1+\frac{x-853}{147}-1\)

\(\Leftrightarrow\frac{x-1000}{855}+\frac{x-1000}{853}-\frac{x-1000}{145}-\frac{x-1000}{147}=0\)

\(\Leftrightarrow\left(x-1000\right)\left(\frac{1}{855}+\frac{1}{853}-\frac{1}{145}-\frac{1}{147}\ne0\right)=0\Leftrightarrow x=1000\)