(2a-3)(3+2a)+[(a-½)²-(a+½)²]×(2a+3)
=(2a-3)(3+2a)+[(a-½+a+½)(a-½-a-½)] ×(2a+3)
=4a²-9-2a×(2a+3)
=4a²-9-4a²-6a
=-9-6a