The equation to the pair of lines passing through origin and perpendicular to 5x2+7xy+y2=0

The combined equation of pair of lines which are perpendicular to the pair of lines ax2+2hxy+by2=0 and passing through the origin is bx2−2hxy+ay2=0Therefore, the combined equation of pair of lines which are perpendicular to the pair of lines 5x2+7xy+y2=0 and passing through the origin is x2−7xy+5y2=0.