（1）4x(x-1)²-9x³
=x[4(x-1)^2-9x^2]
=x(2x-2+3x)(2x-2-3x)
=x(5x-2)(-x-2)
=-x(5x-2)(x+2)
（2）a²-四分之一b²+b-1
=a^2-1/4(b^2-4b+4)
=a^2-1/4(b-2)^2
=1/4[4a^2-(b-2)^2]
=1/4(2a+b-2)(2a-b+2)

（3）(x²+x)²-6(x²+x)
=(x²+x)(x²+x-6)
=x(x+1)(x+3)(x-2)