14с-8b/49c²-16b²=2(7c-4b)/(7c-4b)(7c+4b)=2/7c+4b

18+2b/81-b²=2(9-b)/(9-b)(9+b)=2/9+b

49-16a²/(7+4a)²=(7-4a)(7+4a)/(7+4a)²=7-4a/7+4a

1+12n+36n²/1-36n²=(1+6n)²/(1-6n)(1+6n)=1+6n/1-6n