(1)
(2x+3)(y-1)-(x+1)(2y-3)
=2xy+3y-2x-3-(2xy+2y-3x-3)
=2xy+3y-2x-3-2xy-2y+3x+3
=x+y
(2)
(2a+3b)(2a-3b)(4a^2-9b^2)
=(4a^2-9b^2)(4a^2-9b^2)
=16a^4-72a^2b^2+81b^4