Formula of line segment joining 2 points I've got a question that is probably a bit simple but I can't figure it out sadly.
I read in my textbook that, given 2 points $x,y$ of a set, the line segment that connects these 2 points can be described by the expression 
$$\lambda x + (1-\lambda)y, \lambda \in [0,1]$$
Is there some kind of derivation for this particular formula you can show me? Thanks a lot.
P.S. I don't really know what tags to add so if these two are incorrect please edit freely. 

Rewrite it as $y + \lambda(x-y)$ and recognize $y$ as the 'anchor point' and $(x-y)$ as the vector pointing from $y$ to $x$.
Does this visualization help?
As $\lambda$ varies from $0$ to $1$, one moves from the 'anchor' $y$ along $(x-y)$ until $x$.
