Straight Line Question 114

Question: In what ratio the line $ y-x+2=0 $ divides the line joining the points (3, -1) and (8, 9) [Karnataka CET 2002]

Options:

A) 1 : 2

B) 2 : 1

C) 2 : 3

D) 3 : 4

Show Answer

Answer:

Correct Answer: C

Solution:

  • Given, equation of line $ y-x+2=0 $ and co-ordinates of points $ (x_1,y_1)=(3,-1) $ and $ (x_2,y_2)=(8,9) $ . We know that if the ratio in which a line $ ax+by+c=0 $ is divided by points $ (x_1,y_1) $ and $ (x_2,y_2) $ is $ \lambda :1 $ , then intersecting point $ ( \frac{\lambda x_2+x_1}{\lambda +1},\frac{\lambda y_2+y_1}{\lambda +1} ) $ lies on $ ax+by+c=0 $ . Thus any point on the line joining $ (3,-1) $ and $ (8,9) $ dividing it in the ratio $ \lambda :1 $ is $ ( \frac{8\lambda +3}{\lambda +1},\frac{9\lambda -1}{\lambda +1} ) $ and if it lies on $ y-x+2=0, $ then $ \frac{9\lambda -1}{\lambda +1}-\frac{8\lambda +3}{\lambda +1}+2=0 $ or $ 9\lambda -1-(8\lambda +3)+2(\lambda +1)=0 $ or $ 3\lambda -2=0,\lambda =\frac{2}{3} $ i.e. ratio is $ 2:3 $ .