The coplanar points  3,2,5,2,1,1,−1,4,1,0,5,5 form a

Given points are  A3,2,5,B2,1,1,C−1,4,1,D0,5,5The lengths of the sides AB=1+1+16=18BC=9+9+0=18AC=16+4+16=36BD=4+16+16=36            Observing the adjacent sides  AB,BCare equal, and the lengths of the diagonal are equalDiagonals are equal, and adjacent sides are equal Therefore, the quadrilateral formed by the given vertices is square.