1.（2x^3-4）+（x^2-8x）
=2x^3+x^2-8x-4
=x^2(2x+1)-4(2x+1)
=(2x+1)(x^2-4)
=(2x+1)(x-2)(x+2)
2.x^3-x^2-x+1
=x^2(x-1)-(x-1)
=(x-1)(x^2-1)
=(x-1)(x-1)(x+1)
=(x-1)^2(x+1)
3.4m^2-x^2-9-6x
=4m^2-(x^2+6x+9)
=4m^2-(x+3)^2
=(2m+x+3)(2m-x-3)
4.（x^2-y^2）+（6y-9）
=x^2-y^2+6y-9
=x^2-(y^2-6y+9)
=x^2-(y-3)^2
=(x+y-3)(x-y+3)
5.a^2+2ab+b^2-2a-2b+1
=(a+b)^2-2(a+b)+1
=(a+b-1)^2