Pair of Straight Lines

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

ax2 + 2hxy + by2 + 2gx + 2fy + c = 0, where a, b, c, f, g, h are constants.

Pair of straight lines passing through the origin

The homogeneous equation ax2 + 2hxy + by2 = 0 of second degree in x and y represents a pair of straight lines passing through the origin.