Does the point of intersection of line y = k*x + b and line x = k*y + b have a negative x coordinate?
1) k>0, b>0
when they intercept y=y or x=x
k>0, b>0. x can be negative and positive so insuff.
k>1 then x can be negative or positive depeding on the value of b which can be negative and positive as well so insuff.
combined negative. suff.