The Abelian property or commutativity.
I think that wants to be 16x2 - 40xy + 25y2 That factors to (4x - 5y)(4x - 5y) or (4x - 5y)2
5y + 7 = 25y = -5y = -1
6x plus 3y minus 2x plus 5y equals 4x plus 8y.
It equals x+5y simplified
I do not know how to answer this.