3=-k+b
0=-k√6+b
k=3/(√6-1)=3(√6+1)/5>0
b=3(√6+6)/5
-kx-b≤0
kx>=-b
-b/k=(√6+6)/(√6+1)=(√6+6)(√6-1)/5= (6+6√6-√6-6)/5=√6
x>=√6
｛x|x >=√6 ｝