E 1.Fie z=a+bi lzl=√(a²+b²)=5 dai valori convenabile lui a si b. exemplu a=4 b=3 lzl=√(16+9)=5 z=4+3i
Ex5.(1+i)²+(1-i)²=1+2i+i²+1-2i+i²=2+2i²=2-2=0
E 6.z²=-1=> z=√-1=+/-i
E 7.
Se aplica Viett
S=-(1+i√3+1-i√3)=-2
p=(1+i√3)*(1-i√3)=1-3i²=1+3=4
Ecuatia este: x²-2x+4
E8,Fie z=a+bi zbarat=a-bi Inlocuiesti in ecuatie
a+bi+a-bi+(a+bi)(a-bi)=-1
2a+(a²-b²i²)=-1
2a+a²+b²= -1
Sistem
{a²+2a=-1 => a²+2a+1=0 =>(a+1)²=0=> a=-1
z=-1
