Question

Which factor do 64x^2 + 48x + 9 and 64x^2 - 9 have in common?

Answer 1

Start with the second expression.  That factors easily into (8x-3)(8x+3).
Since 64x^2 + 48x + 9 has no negative signs, I'd bet that the common factor is (8x+3).  Divide  64x^2 + 48x + 9  by that to verify.