4x²-12x-9 = ?
∆ = (-12)² -4•4•(-9) =
= 144 + 144 = 2•12²
x₁,₂ = (12±12√2)/(2•4) = (3±3√2)/2
Deci,
4x²-12x-9 = 4(x - x₁)(x - x₂) =
= 4[x - (3-3√2)/2][x - (3+3√2)/2]=
= (2x-3+3√2)(2x-3-3√2)
