Sa se rezolve, in multimea numerelor complexe, ecuatiile:
a) x² = -9
b) x² - 8x + 25 = 0
c) x² - 2x + 4 = 0
d) x² + 2x + 2 = 0
e) x la a 4a = 16

[tex] a)x^{2} =-9;x=3i;x=-3i \\ b) x^{2} -8x+25=0 \\ [/tex]
Δ=[tex]64-100=-36[/tex]
[tex] x_{1} =\frac{8-6i}{2}=4-3i \\ x_{2}=4+3i [/tex]
[tex]c) x^{2} -2x+4=0[/tex]
Δ=[tex]4-16=-12 \\ x_{1}= \frac{2-2i \sqrt{3} }{2}=1-i \sqrt{3} \\ x_{2}=1+i \sqrt{3} [/tex]
d)[tex] x^{2} +2x+2=0[/tex]
Δ=4-8=-4
[tex] x_{1} =\frac{-2-2i}{2}= -1-i \\ x_{2}=-1+i [/tex]
[tex]e)x^4=16 \\ x_{1}=2; x_{2}=-2; x_{3}=2i; x_{4}=-2i [/tex]