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(2a + 3)(2a – 3)(4a² + 9)

First solving (2a + 3)(2a – 3)

Using the identity (a +b) (a–b) = a² – b²

Here a = 2a and b = 3

= (2a)² –3²

= 4a² – 9

Now (4a² – 9)(4a² + 9)

Using the identity (a +b) (a – b) = a² – b²

Here a = 4a and b = 9

= (4a)² – 9 ²

= 16a⁴ – 81