a) 5x² - 3x + 1 = 0
Δ = 9 - 4 * 5 * 1 = 9 - 20 = -11 ⇒ x ∉ R
b) x² + 11x = 0
Δ = 121 -4 * 1 * 0 = 121 = 11²
x₁ = [tex]\frac{-11 + 11}{2}[/tex] = 0
x₂ = [tex]\frac{-11-11}{2}[/tex] = -11
c) 4x² - 9 = 0 ⇔ (2x - 3)(2x + 3) = 0
2x - 3 = 0 ⇒ x₁ = [tex]\frac{3}{2}[/tex]
2x + 3 = 0 ⇒ x₂ = [tex]-\frac{3}{2}[/tex]
d) 3x² - 5x + 2 = 0
Δ = 25 - 4 * 2 * 3 = 25 - 24 = 1 = 1²
x₁ = [tex]\frac{5 + 1}{6}[/tex] = 1
x₂ = [tex]\frac{5-1}{6}[/tex] = [tex]\frac{4}{6}[/tex] = [tex]\frac{2}{3}[/tex]
