题目已知mmm、nnn是方程x2−2x−1=0{{x}^{2}}-2x-1=0x2−2x−1=0的两根，且(7m2−14m+a)(3n2−6n−7)=8(7{{m}^{2}}-14m+a)(3{{n}^{2}}-6n-7)=8(7m2−14m+a)(3n2−6n−7)=8，则aaa的值为 ((( ))) A.555B.666C.—9—9—9D.999知识点：一元二次方程的概念章节：未标注
