So this would be, instead of f of x minus nine, I'll write x squared minus nine. And x squared minus nine, this is a difference of squares, so this is x plus three times x minus three. X plus three times x minus three. And so these would cancel out. We can say that this equivalent to x plus three, as long as x does not equal three, and that's okay, because we're approaching from the left. And as we approach from the left, well, x plus three is defined for all real numbers, it's continuous for all real numbers, so we can just substitute the three in there. So we would get a six.