Question

A(-1,2,1),B(1,-2,5),C(4,-7,8),D(2,-3,4), is it the vertices of a parallelogram

Answer 1

yes the given vertices is of parallelogram..the length of AD=
$\sqrt{43}$
and the length of its opposite side BC is also the same that is =
$\sqrt{43}$
so we know if the opposite side are same and parallel then ..ut is side of parallelegram