x²-(m²+4)x-2m²-12=0的两根a,b => a+b=m²+4 ;ab=-2m²-12=>(a,0);(b,0)是抛物线y=x²-(m²+4)x-2m²-12图象与x轴的两个交点此两个交点间距离= |a-b|=d ; d²=(a+b)²- ...