x³-5x²-4x+20=0, x²(x-5)-4(x-5)=0, (x-5)(x²-4)=0, (x-5)(x-2)(x+2)=0, x-5=0, x=5 x-2=0, x=2 x+2=0, x=-2 Ответ: -2, 2, 5.