设4XY-AX²-Y²-M=（1-2X+Y)（B+2X-Y)即4XY-AX²-Y²-M=B+2X-Y-2BX-4X²+2XY+BY+2XY-Y²=B+（2-2B）X-4X²+4XY+（B-1）Y-Y²比较系数得2-2B=0,A=4,B-1=0,M=B∴M=1