根据韦达定理
x1+x2=5/3
6x1+x2=0
5x1+x1+x2=0
5x1+5/3=0
x1=-1/3
x2=5/3-(1/3)=5/3+1/3=2
x1x2=a/3
-1/3*2=a/3
a=-2