А)
х² + х = 0
х * (х + 1) = 0
х₁ = 0
х + 1 = 0
х₂ = -1
б)
х² - 4х + 3 = 0
D = 4² - 4 * 1 * 3 = 4 > 0
x₁ = (4 - √4) : (2 * 1) = 1
x₂ = (4 + √4) : (2 * 1) = 3
в)
5х² + 14х - 3 = 0
D = 14² + 4 * 5 * 3 = 196 + 60 = 256 > 0
x₁ = (-14 - √256) : (2 * 5) = -30 : 10 = -3
x₂ = (-14 + √256) : (2 * 5) = 2 : 10 = 2/10 = 0,2