- 1.5(4x + 1)2 4.5 - 2.5(x + 1)?

yes it is.

diagonals of parallelogram bisect each other so if the diagonals are of equal length then they bisect each other and length of each bisect is equal. so the angle made by these bisects with any sides should be equal ( it is a theorem of geometry ) if all such angles are equal then the length all the sides with which these angles are made should of equal.now if all the sides has same length then it is rhombus and here all angles have same values that is x+x+x+x=360; x=90

so it is proved that it is a rectangle.