a) x^2 - 2x + 1 - 1/4 = 0 <=> x^2 - 2x + 3/4 = 0
Δ = 4 - 3 = 1;
x1 = (2 - 1)/2 = 1/2; x2 = (2+1)/2 = 3/2
b) x^2 + 5x = 0 <=> x(x + 5) = 0 <=> x1 = 0; x2 = -5
c) x^2 - 4x >= 0 <=> x(x - 4) >= 0
x1 = 0; x2 = 4
x∈(-niesk, 0> suma <4, +niesk)
