Bonsoir,
4z² +8z + 5 = 0
[tex]\Delta = (8)^{2} - 4 \times 4 \times 5[/tex]
[tex]\Delta = 64 - 80 = -16 = (4i)^{2}[/tex]
[tex]\sqrt\Delta = \sqrt(4i)^{2}[/tex]
[tex]\sqrt\Delta = 4i[/tex]
Z1 = (8 - 4i)/(2 x 4) = (8 - 4i)/8 = 1 - i/2
Z2 = (8 + 4i)/8 = 1 + i/2