Explain how the expression $tX + (1-t)Y$, $0\le t\le 1$, produces a segment that connects point $X (x_1, y_1)$ with point $Y (x_2,y_2)$.
So I rearranged the problem such that $t(X - Y) + Y$ which I gather the $(X-Y)$ to be changes in $x$ and $y$, but I am struggling with the rest of the explanation.