Answers

2016-07-31T18:21:08+08:00
Your friend's not correct.
It's not even a difference between two squares to begin with since it exhibits a plus sign between the two terms.
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2016-07-31T22:13:04+08:00
X² + 16     ↔     this could be a difference of two squares if you introduce
                         the imaginary number      i
  thus
           x² + 16   =  (x + 4i)(x - 4i)
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