a]
x² - 8x + 7 = 0
a = 1, b = -8, c = 7
∆ = (-8)² - 4 * 1 * 7 = 64 - 28 = 36
√∆ = √36 = 6
x = (-(-8) - 6)/(2 * 1) = 2/2 = 1
x = (-(-8) + 6)/(2 * 1) = 14/2 = 7
b]
x² + 10x + 25 = 0
(x + 5)² = 0
x + 5 = 0
x = -5
c]
3x² - 12x = 0 / : 3
x² - 4x = 0
x(x - 4) = 0
x = 0 lub x = 4
d]
4x² - 9 = 0
(2x + 3)(2x - 3) = 0
x = -1,5 lub x = 1,5
