(x-a)/(x-1)-3/x=1两边同乘以x(x-1)得：x(x-a)-3(x-1)=x(x-1)x²-ax-3x+3=x²-x(a+2)x=3x=3/(a+2)∵无解∴a+2=0，或3/(a+2)=1a=-2，或a=1
