(1)原式=(2x+3y)³-9x²y²(2x+3y)
=(2x+3y)[(2x+3y)²-9x²y²]
=(2x+3y)(2x+3y+3xy)(2x+3y-3xy)
(2 x²-y²+4x-2y+3
=(x²+4x+4)-(y²+2y+1)
=(x+2)²-(y+1)²
=(x+2-y-1)(x+2+y+1)
=(x-y+1)(x+y+3)