In parallelogram abcd angle b is a right angle determine whether the parallelogram is a rectangle if so by what property

If a parallelogram has at least one 90 degree angle then its opposite angle is equal and also = 90 degrees.  

The 2 remaining opposite angles add up to 180 degrees and since they must be equal, they must be 90 degrees each.

So, we have a quadrilateral with four 90 degree angles and is therefore a rectangle OR it could possibly be a square.

Step-by-step explanation:

80x^8−68x^6+16^5−20x^4−4x^3+8x^2

hope i'm right lol