24) D

Let us first solve the first part of the problem


2x + 3     +      2x – 3
 2x – 3             2x + 3


(2x + 3)²   +   (2x – 3)²
    (2x – 3) (2x + 3)


(4x² + 6x + 9)   +   (4x² – 6x + 9)
                   4x² – 9

8x² + 18
 4x² – 9

Let us now solve the second part of the problem

8x² + 18   –    2
 4x² – 9          1

8x² + 18   –    8x² – 18
 4x² – 9           4x² – 9

8x² + 18 – (8x² – 18)
        4x² – 9

8x² + 18 – 8x² + 18
        4x² – 9

18 + 18
 4x² – 9

    36
 4x² – 9

Remember that we solved (2x – 3) (2x + 3) = 4x² – 9

So the answer is :

          36
(2x – 3) (2x + 3)