Here is one of my problems that I am struggling with:
FACTOR x to the 4th power - 9y squared
Then is says "1. x to the 4th power = (x squared) squared, and 9y squared = (3y) squared." I understand that.
And then it says "2. x to the 4th power - 9y squared = (x squared) squared - (3y) squared." I understand that, too, because I just said those were equal.
THEN, suddenly, it says it says, "3. And so, x to the 4th power - 9y squared = (x squared + 3y)(x squared - 3y). Solved"
WHERE did that come from??? Can someone please explain why (x squared) squared - (3y) squared turns into (x squared + 3y)(x squared - 3y)???