2х/(х+3)-х/(3-х)=9/(4х^2-36) решить уравнение(с подробным решением)

Переносим все в одну сторону 
2х/(х+3)-х/(3-х)-9/(4х²-36)=0
2х/(х+3)-х/(3-х)-9/4(х-3)(х+3)
приводим к общему знаминателю
первую дробь умнажаем на 4(х-3); вторую дробь на 4(х+3); 
(8х²-24х-4х²+12х-9)/4(х+3)(х-3)=0
в числители приводим подобные
(4х²-12х-9)/4(х+3)(х-3)=0
числитель равен нулю, а знаменатель не равен нулю
4(х+3)(х-3)≠0
х≠3 и х≠-3
4х²-12х-9=0
Д=144+4×4×9=288
√Д=√288=12√2
х=(12-12√2)/8=(3(1-√2))/2 
х=(3(1+√3)/2

Unit 4 Eating Out

Match the words in A with its explanation in B

1.a quality a) no good

2. abundant b) large quantities

3. customary c) to add to a dish to make it look

attractive

4. distinctive d) how good or bad something is

5. to garnish e) quickly

6.interior f) usual

7. inferior g) inside of building

8. relatively h) usual

9. rapidly i)comparatively

II. Complete the sentences with the above words:

1. design is the art of planning the decoration of the inside a house or an

office

4. These shoes are f good .

5. She made progess and was soon the best in the class.

6. thedi with parsley and serve!

7. We look a supply of food with us when we went hiking in the

mountains

8. He’s a good tennis player.

9. This sauce has a very taste.

Объяснение: Unit 4 Eating Out

Match the words in A with its explanation in B

1.a quality a) no good

2. abundant b) large quantities

3. customary c) to add to a dish to make it look

attractive

4. distinctive d) how good or bad something is

5. to garnish e) quickly

6.interior f) usual

7. inferior g) inside of building

8. relatively h) usual

9. rapidly i)comparatively

II. Complete the sentences with the above words:

1. design is the art of planning the decoration of the inside a house or an

office.

2. It’s to hold the door open for someone who is entering a building

behind you.

3. They were very upset. They had bought goods of quality.

4. These shoes are of good .

5. She made progress and was soon the best in the class.

6. the dish with parsley and serve!

7. We look an supply of food with us when we went hiking in the

mountains.

8. He’s a good tennis player.

9. This sauce has a very taste.

Пусть х км/ч - скорость катера в стоячей воде
Тогда (х+2) км/ч - скорость катера по течению реки
(х-2) км/ч - скорость катера против течения реки
5(х+2) км - расстояние, пройденное катером по течению реки
7(х-2) км - расстояние, пройденное катером против течения реки
По условию задачи: катер одинаковое расстояние по течению и против течения реки
Уравнение:
5(х+2) = 7(х-2)
5х+10 = 7х-14
5х-7х = -14-10
-2х = -24
х = -24:(-2)
х = 12

скорость катера в стоячей воде 12 км/ч
5*(12+2) = 5*14 = 70 км - проплыл катер по течению реки