`2/8 = 9/36`

`2/9=8/36`

`36/8=9/2`

`36/9=8/2`

`8/2=36/9`

`8/36=2/9`

`9/2=36/8`

`9/36=2/8`

`12-6x=0`

`12=6x`

`x=12:6`

`x=2`

`sin^2x+cos^2x=1`

`<=>sin^2x+(1/2)^2=1`

`<=> sinx=\pm \sqrt3/2`

• `sinx=\sqrt3/2 => P=3. (\sqrt3/2)^2 +1=13/4`

• `sinx=-\sqrt3/2 => P = 3.(-\sqrt3/2) +1=13/4`

`=>` A.

`tan a =3 <=> (sina)/(cosa) =3 <=> sina=3cosa`

Có: `sin^2a+cos^2a =1`

`<=> (3cosa)^2 + cos^2a =1`

`<=> 10cos^2a =1`

`<=> cosa = \pm \sqrt10/10`

`=>` A.

`HCl+ Zn → H_2 +ZnCl_2`

`0,65..0,65...0,65...0,65`

- Sửa 1 chút:

Bill works ..................... his brother.

A. as successfully as     B. so successfully as     C. successfully than

He is ..................... football player in this city.

A. the best     B. the worse     C. the goodest

Bill works ..................... his brother.

A. as successfully as     B. so successfully as     C. successfully than

 Mount Everest is ..................... highest mountain in the world.

A. as     B. more     C. the

..................... all the countries in the world, Vatican is the smallest.

A. in     B. Of     C. the

Jenny behaves ..................... than Helen.

A. kinder     B. more kindly     C. as kindly as

However + adj/adv + S + V, S + V

1. Although he is so young, his acting is excellent.

2 Despite the fact that it was noisy, the children slept well.

3. All critics said this film is really boring, I was so interested in it nevertheless.

4. In spite of its fascinating poster, I don't want to see this film.

5. However carefully she prepared for the casting, she made some mistakes

6. Despite our careful plan, we made some mistakes.

Gọi `a/7` là phân số cần tìm.

Khi cộng tử với 16, nhân mẫu với 5 thì phân số không đổi:

`(a+16)/(7.5)=a/7`

`(a+16)/(7.5)=(a.5)/(7.5)`

`a+16=a.5`

`16=a.5-a`

`16=a.(5-1)`

`16=a.4`

`a=16:4`

`a=4`