Show that the points (a, 0), (0, b) and (3a, -2b) are collinear. Also find the equation of the line containing them.
Let A(a, 0), B(0, b) and C(3a, -2b) and C(3a, -2b) be the given points.
Then, the equation of line AB is given by y−0x−a=b−00−a⇒−ay=bx−ab
⇒bx+ay−ab=0
Thus, the equation of line AB is bx+ay−ab=0 .............(i)
Putting x = 3a and y=−2b in (i), we get LHS =
b.3a+a(−2b)−ab=3ab−2ab−ab=0=RHS
Thus, the point C(3a,−2b) also lies on AB.
Hence, the given points are collinear and the equation of the line containing them is bx+ay−ab=0