Question

What property of real numbers is being used in the following (x+a)(x+b)=(x+a)x + (x+a)b ?

Answer 1

The distributive property. If we expand it, we get (x)(x+a)+b(x+a) by separating the variables in (x+b) 

Answer 2

Distributive property. It shows that the first is being multiples the second.