Find the value of K in a specific case of a cartesian plane I have a linear equation of a line in a cartesian plane $r:= \{(x,y) \in \mathbb{R}^2 \mid kx-(k+1)y+k-1=0, \,\, k \in \mathbb{R}\}$ 
and I have to find the value of k so that the line intersects the x axis in a x positive point.
Any tips?

Straight line in intercepts form:
$$ \dfrac{x}{(1-k)/k} +\dfrac{y}{(k-1)/k+1} = 1 $$
If k<1 positive x- intercept
If k=1 line through origin
If k>1 negative x- intercept
