x^4-6x^3+13x^2-12x+k=(x²+mx+n)²=x^4+m^2x^2+n^2+2mx^3+2nx^2+2mnx=x^4+2mx^3+(m^2+2n)x^2+2mnx+n^2比较系数,得:2m=-6m^2+2n=132mn=-12n^2=k分别解得:m=-3n=2k=4