The straight line x+2y−9=0,3x+5y−5=0 and ax+by−1=0 are concurrent if the straight line 35x−22y+1=0 passes through the point
(a,b)
(b,a)
(a,−b)
(−a,b)
The three lines are concurrent if
1 2 −93 5 −5a b −1=0
⇒35a−22b+1=0⇒35x−22y+1=0 passes through (a, b)