The equation of the bisectors of the angle between the lines given by ax2 + 2hxy + by2 = 0 is
x2−y2
a−b
=
xy
h
... (i) And the equation of the bisectors of the angle between the lines given by a2x2 + 2h (a + b) xy + b2y2 = 0 is
x2−y2
a−b
=
xy
h(a+b)
⇒
x2−y2
a−b
=
x
h
... (ii) From eqs. (i) and (ii), it is clear that both the pair of straight lines have the same bisector, hence, the given two pairs of straight lines are equally inclined.