Linear function
Example: X=(–1,1)+t(2,3), t∈R is a line in vector form. Here: a1=2, a2=3, x1=–1 and x2=1. The line goes through the points (x1,y1)=(–1,1) and (x1+a1,y1+a2)=(1,4). The corresponding parametric form of this line is: x(t)= –1+2t, y(t)=1+3t.  The unique slope-intercept form of this line is: y(x)=1.5x+2.5   (solve the first equation for t and substitute this result into the second equation).