①a²-b²-2b-1
=a²-(b+1)²
=(a+b+1)(a-b-1)
②a四次方-9-6b-b²
=a^4-(3+b)²
=(a²-3-b)(a²+3+b)
③ x三次方+2xy-x-xy²
=x(x²-y²-1+2y)
=x[x²-(y-1)²]
=x(x-y+1)(x+y-1)