y'=4x³+6x²+12x+5=04x³+2x²+4x²+12x+5=02x²(2x+1)+(2x+5)(2x+1)=0(2x²+2x+5)(2x+1)=02x²+2x+5=0无解所以2x+1=0x=-1/2令z=4x³+6x²+12x+5z'=12x²+12x+12=12(x...