Answer:
Step-by-step explanation:
a) 4x² + 20 = 0
4x² = -20
x² = -20/4
x² = -5 = i² *5
x = √i²5
x = i√5
b) 4x² + 5 = -7
4x² = -7 - 5
4x² = - 12
x² = -12/4
x² = -3 = 3i²
x = i√3
c) x² + 4x + 20 = 0
a = 1 ; b =4 ; c =20
[tex]x = \frac{-b+\sqrt{b^{2}-4ac}}{2a} and \frac{-b-\sqrt{b^{2}-4ac}}{2a};\\\\x = \frac{-4+\sqrt{16-4*1*20}}{2*1} and\frac{-4-\sqrt{16-4*1*20}}{2*1}\\\\=\frac{-4+\sqrt{16-80}}{2} and \frac{-4-\sqrt{16+80}}{2}\\\\=\frac{-4+\sqrt{-64}}{2} and \frac{-4-\sqrt{64}}{2}\\\\= \frac{-4+8i}{2} and\frac{-4-8}{2}[/tex]
= (-2 +4i) & -12/2
= (-2 + 4i) and (-6)
