My approach to this was to manipulate the QC, so I squared both sides. This would make the answer C. Obviously this isn’t the right answer. Why can’t I use QC manipulation? I don’t fully understanding greg’s absolute value reasoning and why squaring both sides leads to a different answer.
Try a negative value for a.
If I square both sides though, I get the exact same formula on both (a^2 - 6a +9), so negative or positive the answer is the same.
The problem is that squaring can change the range and the domain so you must consider the original expression.