Sides of the triangle are x−3y=0, 4x+3y=5 and 3x+y=0
By seeing the equation of the sides we can easily find out that x−3y=0 and 3x+y=0 are perpendicular to each other.
So, they will cut each other at orthocentre.
Solving x−3y=0 and 3x+y=0,
we find x=0, y=0.
When we put x=0, y=0 in 3x−4y=0,
we find 0=0 (satisfied).
So, line 3x−4y=0 passes through orthocentre.