(3a+2b)(3a-3b)-(a-2b)(2a-b)
=9a²-3ab-6b²-2a²+5ab-2b²
=7a²+2ab-8b²
=7×(-1.5)²+2×(-1.5)×1/4-8×(1/4)²
=31.5-0.75-0.5
=30.25