Straight Lines and Pair of Straight Lines

(a,b) is the point to which the origin has to be shifted by translation of axes so as to remove the first-degree terms from the equation 2x2−3xy+4y2+5y−6=0. If the angle by which the axes are to be rotated in positive direction about the origin to remove the xy-term from the equation ax2+23abxy+by2=0 is θ, then tan‌2‌θ=