1.4x^4y²-5x²y²-9y²
=y²(4x^4-5x²-9)
=y²(4x²-9)(x²+1)
=y²(x²+1)(2x+3)(2x-3)
2.2（a-b）²-（a-b）-3
=[2(a-b)-3][(a-b)+1]
=(2a-2b-3)(a-b+1)
3.4（2x+y）²-8（2x+y）+3
=[2(2x+y)-1][2(2x+y)-3]
=(4x+2y-1)(4x+2y-3)
]
4.7x^4+5x²y²-2y^4
=(x²+y²)(7x²-2y²)
5.5x³y-7x²y-6xy
=xy(5x²-7x-6)
=xy(5x+3)(x-2)