The equation of a pair of straight lines is in the form

**ax ^{2} + 2hxy + by^{2} + 2gx + 2fy + c = 0**, where a, b, c, f, g, h are constants.

**Pair of straight lines passing through the origin**

The homogeneous equation ax^{2} + 2hxy + by^{2} = 0 of second degree in x and y represents a pair of straight lines passing through the origin.