x³-16x²+64x-75=0x³-3x²-13x²+64x-75=0(x³-3x²)-(13x²-64x+75)=0x²(x-3)-(13x-25)(x-3)=0(x-3)(x²-13x+25)=0x-3=0或x²-13x+25=0x=3，x=(13-√69)/2，x=(13+√69)/2
