ax1+bx2+2x3=1,① (b-1)x2+x3=0,②ax1+bx2+(1-b)x3=3-2b,③①-③,(b+1)x3=2(b-1),方程有解,∴b≠-1,x3=2(b-1)/(b+1),代入②,(b-1)x2+2(b-1)/(b+1)=0,b=1时x2为任意数,b≠1时x2=-2/(b+1),代入①,ax1+(2b-4)/(b+1)=1,ax1=(5-b)/(b+1),a=0,b=5时x1为任意数,a≠0时x1=(5-b)/[a(b+1)].