Straight Line Question 210

Question: The combined equation of the pair of lines through the point (1, 0) and parallel to the lines represented by $ 2x^{2}-xy-y^{2}=0 $ is

Options:

A) $ 2x^{2}-xy-y^{2}-4x-y=0 $

B) $ 2x^{2}-xy-y^{2}-4x+y+2=0 $

C) $ 2x^{2}+xy+y^{2}-2x+y=0 $

D) None of these

Show Answer

Answer:

Correct Answer: B

Solution:

  • [b] We have the equation $ 2x^{2}-xy-y^{2}=0 $

$ \Rightarrow (2x+y)(x-y)=0 $ If $ (h,k) $ be the point then remaining pair is $ (2x+y+h)(x-y+k)=0 $ Where, $ 2x+y+h=0 $ and $ x-y+k=0 $ It passes through the point (1, 0)
$ \therefore 2\times 1+0+h=\Rightarrow 2+h=0\Rightarrow h=-2 $ and $ 1-0+k=0\Rightarrow 1+k=0\Rightarrow k=-1 $

$ \therefore $ Required pair is $ (2x+y-2)(x-y-1)=0 $

$ \Rightarrow 2x^{2}-2xy-2x+xy-y^{2}-y-2x+2y+2=0 $

$ \therefore 2x^{2}-xy-y^{2}-4x+y+2=0 $