①原式=3x²+(5y+1)x-(2y²-9y+4)
=3x²+(5y+1)x-(y-4)(2y-1)
=[3x-(y-4)][x+(2y-1)]
=(3x-y+4)(x+2y-1)
②原式=4b²+(4c-10)b+c²-5c+6
=4b²+(4c-10)b+(c-2)(c-3)
=(2b+c-2)(2b+c-3)
③原式=x²+(y+3)x-(2y²-3y-2)
=(x+2y+1)[x-(y-2)]
=(x+2y+1)(x-y+2)
①原式=3x²+(5y+1)x-(2y²-9y+4)
=3x²+(5y+1)x-(y-4)(2y-1)
=[3x-(y-4)][x+(2y-1)]
=(3x-y+4)(x+2y-1)
②原式=4b²+(4c-10)b+c²-5c+6
=4b²+(4c-10)b+(c-2)(c-3)
=(2b+c-2)(2b+c-3)
③原式=x²+(y+3)x-(2y²-3y-2)
=(x+2y+1)[x-(y-2)]
=(x+2y+1)(x-y+2)