x+3/1=2x+x/2+12=3/2xx=4/3.---------------------------x+1/3=2x+2/x+1x*x+1/3x=2x*x+2+xx*x+2/3x+2=0y=x*x+2/3x+2 求导y'=2x+2/3令y'=2x+2/3=02x=-2/3x=-1/3当x=-1/3时y有极小值为29/18则x*x+2/3x+2=0在有理数集内无解。解一元两次方程的十字交叉给忘了````