A quadrilateral has vertices, taken in order, at P(3, 0), Q(4, 5), R(−1, 4) and S(−2, −1). Which description of this quadrilateral is correct?

All four sides come out equal: PQ = √(1 + 25) = √26, QR = √(25 + 1) = √26, RS = √(1 + 25) = √26 and SP = √(25 + 1) = √26. Four equal sides make it a rhombus. It is not a square because the diagonals are unequal: PR = √(16 + 16) = √32 while QS = √(36 + 36) = √72.