Question

Решите уравнение:
1) (x-12)(3x+9)=0
2) (x+2)^2=0
3) x^2+7x=0
4)x^2-25=0

Answer 1

1)
3x^2 + 9x - 36x - 108 = 0
3x^2 - 27x - 108 = 0
x^2 - 9x - 36 = 0
D = 81 + 144 = 225
x1 = (9 + 15)/2 = 12
x2 = (9 - 15)/2 = -3
2)
x + 2 = 0
x = -2
3)
x( x + 7) = 0
x = 0 или x+7 = 0 
               x = -7
4)
(x-5)(x+5) = 0
x-5 = 0 или x+5 = 0
x = 5          x = -5