1) x^2 + 11x = 0
2) 3x^2 - 35 = 0
3)x^2 + 64 = 0

1) x^2 + 11x = 0
x(x + 11) = 0
x = 0
x + 11 = 0
x = - 11

2) 3x^2 - 35 = 0
D = b^2 - 4ac = 0 + 420 = 420
x1,2 = +/- √420 / 6

3) x^2 + 64 = 0
x^2 = - 64 - корней нет.