12-27-2022, 01:26 PM
12-27-2022, 01:48 PM
It is just a rule that you need to know. To explain it, you can imagine that (a + b)^2 is equal to (a + b) x (a + b). If we were to multiply everything out, we would get a^2 + ab + ba + b^2 and that would give us a^2 + 2ab + b^2.