9a²-b²-6a+1
=(9a²-6a+1)-b²
=(3a-1)²-b²
=(3a-1+b)(3a-1-b)
(ab+1)²-(a+b)²
=(ab+1+a+b)(ab+1-a-b)
=(a+1)(b+1)(a-1)(b-1)