3)
a) 3a²x-6ax²=3ax(a-2x)
b)(x+3)²-2x-6=(x+3)²-2(x+3)=(x+3)(x+3-2)=(x+3)(x+1)
c)x³+x²-9x-9=x²(x+1)-9(x+1)=(x+1)(x²-9)=(x+1)(x-3)(x+3)
d)x²-y²+4x+4=x²+4x+4-y²=(x+2)²-y²=(x+2-y)(x+2+y)
e)x²-9x+18=x²-6x-3x+18=x(x-6)-3(x-6)=(x-6)(x-3)
f)x⁴+x²+1=x⁴+2x²+1-x²=(x²+1)²-x²=(x²+1-x)(x²+1+x)=(x²-x+1)(x²+x+1)
