Calculate a point on the line at a specific distance . I have two points which make a line $l$ , lets say $(x_1,y_1) , (x_2,y_2)$ . I want a new point $(x_3,y_3)$ on the line $l$ at a distance $d$ from $(x_2,y_2)$ in the direction away from $(x_1,y_1)$ . How should i do this in one or two equation . 

$(x_3,y_3)\in l$ 
The points must be collinear so they form a triangle with surface area $0$ so 
$$x_1(y_2-y_3)+x_2(y_3-y_1)+x_3(y_1-y_2)=0$$
$$d=\sqrt{(x_3-x_2)+(y_3-y_2)}$$
