If the pair of straight lines `xy - x - y +1=0` & the line `ax+2y-3=0` are concurrent then `a =`

Options

A. `-1`
B. 0
C. 3
D. 1

Answer

D

Explanation

Equation of pair of straight line is
`xy-x-y+1=0`
`rArr x-1=0 or y-1=0`
The intesection point of `x-1=0` and `y-1=0` is (1,1)
`:.` Lines `x-1=0,y-1=0 and ax+2y-3=0` are concurrent.
`:.` The interescting point of first two lines lies on the third line
`ax+2y-3=0`
`rArr a+2-3=0 rArr a=1`