即3a-4和-a+6是相反数所以3a-4=-(-a+6)=a-62a=-2a=-1所以m=(3a-4)²=49原式=3a(a+b-12b²)是南京到什么
=（1-1/2)(1+1/2)(1-1/3)(1+1/3)=(1/2)(3/2)(2/3)(4/3)=(1/2)(4/3)=2/3
