(x+2)^2-4x=0... x^2+4x+4-4x=0... x^2+4=0...
∆=b^2-4ac
∆=0^2-4•1•4
∆=-16
Cum delta < 0 ecuatia nu admite solutii reale, dar admite solutii complexe:
x1,2=(-b+ sau - i√-∆)/2a
x1=(i√16)/2...x1=4i/2...x1=2i
x2=(-i√16)/2...x2=-4i/2...x2=-2i
S={-2i,2i} fiind solutii complexe.
