Let p(x1,y1) be a point and t(a,b) be its image about a line Ax+By+C=0 . Now we have a relation,x1-a/A = y1-b/B = -2(Ax1+By1+C)/A^2+B^2 . From this u can find out a and b but this is a use less shit. If u know the distance from the line to the point then u can use parametric equation . This is a good methode to find the image. U know the line so u can get the equation of line perpendicular to it passing throug the given point and u also know the distance than use parametric equation (x1+-rcos@,y1+-rsin@) where x1 y1 is the point of intersection of the given line and the perpendicular to it. And r is the distance of point of intersection and the given point and @ is the slop of perpendicular line .