m=6吧x^-y^2+5x+y+m→(x^2+5x+25/4)-(y^2-y+1/4)-25/4+1/4+m→[(x+5/2)^2-(y-1/2)^2]-6+m→(x+5/2+y-1/2)(x+5/2-y+1/2)-6+m→(x+y+2)(x-y+3)-6+m→m=6 这个方法好像比较简便.考试时候可以用~