1) 4x²-(1/9b²)=(4x²*9b²-1)/(9b²)=((2x*3b)²-1²)/(3b)²=(2x*3b-1)(2x*3b+1)/(3b)².
2) 2x-(1/3b)=(2x*3b-1)/(3b).
3) (2x*3b-1)(2x*3b+1)/(3b)²:(2x*3b-1)/(3b)=(2x*3b+1)/(3b)=(6xb+1)/(3b).
