（x-2)(x-n)=x²-(n+2)x+2n=x²-4x+m所以-(n+2)=-42n=m所以n=2m=2n=4
(x-2)(x－n)=x^2-(n+2)x+2nn+2=4m=2n解得m=4n=2
x^2-4x+m=x^2-(2+n)x+2n2+n=4 m=2nn=2.m=4
