The equation of the straight lines are 3x − 4y + 7 = 0 ... (1) and − 12x − 5y + 2 = 0 ... (2) Here (3) ( − 12) + ( − 4) ( − 5) + (7) (2) = − 36 + 20 + 14 = − 2 < 0. ∴ it makes acute angle. ∴ equation of the bisector of an acute angle between these lines is