5.65 Решите уравнение: a) 7(3x + 6) - (20x + 4) = 0; б) -6(4x - 3) + (7 - 6x) = 0; в) -5(3у + 3) + 2(7y - 6) = 0; г) 6(5 – 4x) + 5(5x + 5) = 9.

Ответ: a) x = 2; б) x = 1; в) y = -27/1 = -27; г) x = -56/1 = -56

a)

7(3x + 6) - (20x + 4) = 0

21x + 42 - 20x - 4 = 0

x + 38 = 0

x = -38

б)

-6(4x - 3) + (7 - 6x) = 0

-24x + 18 + 7 - 6x = 0

-30x + 25 = 0

-30x = -25

x = 25/30 = 5/6

в)

-5(3y + 3) + 2(7y - 6) = 0

-15y - 15 + 14y - 12 = 0

-y - 27 = 0

-y = 27

y = -27

г)

6(5 – 4x) + 5(5x + 5) = 9

30 - 24x + 25x + 25 = 9

x + 55 = 9

x = 9 - 55 = -46

Ответ: a) x = -38; б) x = 5/6; в) y = -27; г) x = -46

Ответ: a) x = 2; б) x = 1; в) y = -27/1 = -27; г) x = -56/1 = -56