Răspuns :
[tex] x^3-4x = 0 \Rightarrow x(x^2-4) = 0 \\ \\ x_1 = 0 ~\text{sau } x^2-4 = 0 \Rightarrow x^2 = 4 \Rightarrow x = \pm 2\Rightarrow x_2 = -2, x_3 = 2\\ \\ S = x_1+x_2+x_3 =0+2-2 = 0 \Rightarrow \boxed{S=0} [/tex]
[tex] x^3-4x = 0 \Rightarrow x(x^2-4) = 0 \\ \\ x_1 = 0 ~\text{sau } x^2-4 = 0 \Rightarrow x^2 = 4 \Rightarrow x = \pm 2\Rightarrow x_2 = -2, x_3 = 2\\ \\ S = x_1+x_2+x_3 =0+2-2 = 0 \Rightarrow \boxed{S=0} [/tex]