The answer it’s a. Pretty sure if not sorry
If 2 sets are disjoint means they have not any common element.
Draw a rectangle & inscribe inside this rectangle 2 circles that do not intersect.
cercle₁ ∩ cercle₂ =Ф.
Their complement would be the part of the rectangle - the 2 circles
Check the picture below.
if you go from the slant height, the path is shorter to the top, since the hypotenuse is the longest of all sides in a right-triangle.
that said, is shorter but is also steeper, so the lateral edge is longer but less steep and thus a bit simpler though longer, but we're only asked on which is shorter.
The answer is -3x^2+10xy+8y^2