This is the commutative property. This is because the commutative property just moves stuff around for example a+b = b+a, is the commutative property. The associative property is a+(b+c) = (a+b)+c, the distributive property is a(b+c) = ab+ac, and the opposite of a sum property is -(a+b) = (-a)+(-b).
i feel like u are going to delete this but if this helped please don't delete it the answer is, Simon is correct because even though the input values are opposite in the reflected function, any real number can be an input.
