x1>0,x2>0
则x1+x2>0
x1x2>0
韦达定理
x1+x2=(3k-1)/k>0
k(3k-1)>0
k<0,k>1/3
x1x2=1>0,成立
判别式大于等于0
9k²-6k+1-4k²>=0
5k²-6k+1=(5k-1)(k-1)>=0
k<=1/5,k>=1
所以k<0,k>=1