I have line segment from

Start Point ($x1$,$y1$) = (279,268) and End Point
($x2$,$y2$) = (281,198)

I want to increase the length of line by 5, 10, 20 etc in end point direction.

i.e value of $y2$ should decrease like 198 -> 193 -> 183 - 163 etc.

Is there any formula through which i can get new values of ($x2$,$y2$) by providing the increase in length constant c (5, 10, 20)?

Thanks