The lines x + 2y + 3 = 0, x + 2y - 7 = 0, and 2x - y - 4= 0 are the sides of a square. The equation of the remaining side of the square can be

Distance between .x + 2y + 3 = 0 and x + 2y -7 =0 is 10/5. Let the remaining side parallel to 2x - y - 4 =0 be 2x−y+λ=0. We have|λ+4|5=105 or λ=6,−14Thus, the remaining side is2x - y + 6=0 or 2x - y - 14=0.