Решите уравнения: 1) (7-х)(5х+1)=0 2) 4х^2+20х=0

1) (7-х)(5х+1)=0
35x + 7 - 5x^2 - x = 0
-5x^2 + 34x + 7 = 0 | : 1
5x^2 - 34x - 7 = 0
5x^2/5 - 34x - 7*5 = 0
x -> a
a^2 - 34a - 35 = 0
a1 = 35
a2 = -1
x1 = 35/5 = 7
x2 = -1/5 = -0,2
 ответ : 7; -0,2;
2) 4х^2+20х = 4x(x+5) = 0
4x = 0
x = 0
 и
x+5 = 0
x = -5
ответ : 0; -5