y = x^2 - x - 6
a = 1, b = -1, c = -6
∆ = b^2 - 4ac
∆ = (-1)^2 - 4•1•(-6) = 1 + 24 = 25
\|∆ = \|25 = 5
x1 = (-b-\|∆)÷2a = -(-1)-5/2•1 = 1-5/2 = -4/2 = -2
x2 = (-b+\|∆)÷2a = -(-1)+5/2•1 = 1+5/2 = 6/2 = 3
\| oznacza pierwiastek drugiego stopnia
