(Note both factors under the original square root are positive.)
(Note that square root sign always means the POSITIVE square root.)
(Note that x negative, so |x| = -x.)
Please explain to me how:
becomes
Bringing 16x^{2} out from the radical becomes negative because x is approaching negative infinity? I don't quite understand why the other coefficients would not automatically become negative, or more importantly why is this one an exception??. Is there some vast concept at work here, or should I just devote this "rule" to route memorization?