Condition to represent pair of lines circle and conic

Which of the following equations represents a pair of real and coincident straight lines?

Which of the following equation does not represent a pair of lines ?

Which of the following equation does not represent a pair of lines ?

What is the General equation of second degree and condition for represent pair of lines?

Under what condition do > represent direction cosines of a line ?

Write an equation representing a pair of lines through the point (a , b) and parallel to the coordinate axes.

If 3x^(2)-6xy-by^(2)=0 represents a pair of lines inclined at an angle pi then b=

Which of the following represents pair of lines?

Position of point wrt to circle, line of circle , Condition of tangency