If each of the points ( x1 , 4) and (-2,y1) lies on the line joining the points (2,-1) and (5,-3), then the point P(x1 , y1 ) lies on the line
x=3y
x=−3y
y=2x+1
2x+6y+1=0
The equation of the line joining (2,-1) and (5,-3) is
2x+3y=1
Since x1,4 and −2,y1 lie on 2x+3y=1.
x1=−11/2 and y1=5/3
Clearly, Px1,y1=P(−11/2,5/3) lies on 2x+6y+1=0.