Question

2. Упростите выражение:а) 6+4а-5а+а-7а    б) 5(р-2)-6(р+3)-3(2р-9)     3. Решите уравнение 0,8(х-2)-0,7(х-1) = 2,74.          Туристы путь в 270 км проделали, двигаясь 6ч на теплоходе и 3ч – на автобусе. Какова была скорость теплохода, если она вдвое меньше скорости автобуса?               5. Найдите корни уравнения (4,9+3,х)(7х-2,8) = 0

Answer 1

1.а) 6+4а-5а+а-7а=-1   
б)5(р-2)-6(р+3)-3(2р-9)=5р-10-6р-18-6р+27=-1-11p 
2. Пусть x-скорость теплохода.
Тогда 2x-скорость автобуса.

6x-путь пройденный теплоходом.

3*2х-путь пройденный автобусом.

6х+6х=270270/12=22,5 км/ч

 Ответ: 22,5 км/ч  

3.

Answer 2

а) 6 + 4a - 5a + a - 7a = 6 - 7a

б) 5(p - 2) - 6(p + 3) - 3(2p - 9) = 5p - 10 - 6p - 18 - 6p + 27 = -7p - 1

3. 0.8(x - 2) - 0.7(x - 1) = 2.74 0.8x - 1.6 - 0.7x + 0.7 = 2.74 0.1x - 0.9 = 2.74 0.1x = 3.64 x = 36.4

4. Let's denote the speed of the bus as v. Then the speed of the boat is 0.5v, since it is half the speed of the bus. We know that the total distance covered by the tourists is 270 km, and the time spent on the boat and on the bus is 6 hours and 3 hours, respectively. Therefore, we can set up the following equation:

6(0.5v) + 3v = 270

Simplifying and solving for v, we get:

3v + 3v = 270 6v = 270 v = 45

Therefore, the speed of the boat is 0.5v = 22.5 km/h.

5. The equation (4.9 + 3x)(7x - 2.8) = 0 has two factors, (4.9 + 3x) and (7x - 2.8), whose product is zero. Therefore, either (4.9 + 3x) = 0 or (7x - 2.8) = 0.

If (4.9 + 3x) = 0, then 3x = -4.9, and x = -4.9/3.

If (7x - 2.8) = 0, then 7x = 2.8, and x = 2.8/7.

Therefore, the solutions to the equation are x = -4.9/3 and x = 2.8/7.