In the “Algebraic Identities (1,2,3,4)” lesson from prepswift, the rule 3 states that (a+b)^2 = a^2 + 2ab + b^2 . However, in the “Common Exponent Mistakes” lesson it states that when you have (a+b)^2 don’t distribute the exponent to (a) and (b).
So my question is why are there two different approaches to that expression and how do you know when to take certain approach?
To clarify, the mistake “distributing to a and b” would be to take (a+b)^2 and expand it as;
a^2 + b^2
This is the mistake you’re being told to avoid as it’s an easy mistake to make when you don’t understand that you need to FOIL (a+b)(a+b).
The correct expression would be;
a^2 + 2ab + b^2
There is only one way to correctly approach it, the second way, by FOILing