Points (3, 3), (h, 0), (0, k) are collinear and ah+bk=13. Then
(3)
Points (3,3), (h,0) and (0,k) are collinear, so one point will lie on the line joining the other two points.
i.e. y-0=k-00-h(x-h)
∴ 3=-kh(3-h) (∵ (3,3) lies on the line)
⇒ 3h+3k=1⇒1h+1k=13
Comparing with ah+bk=13, we get a=1, b=1