1)4b/(2b-1)(2b+1)+(2b+1)/3(2b-1)+(2b-1)/2(2b+1)=
=[6*4b+(2b+1)(4b+2)+(2b-1)(6b-3)]/6(2b-1)(2b+1)=
=(24b+8b²+4b+4b+2+12b²-6b-6b+3)/6(2b-1)(2b+1)=
=(20b²+20b+5)/6(2b-1)(2b+1)=5(4b²+4b+1)/6(2b-1)(2b+1)=
=5(2b+1)²/6(2b-1)(2b+1)=5(2b+1)/6(2b-1)
2)12/(2b+1):5(2b+1)/6(2b-1)=12/(2b+1)*6(2b-1)/5(2b+1)=72(2b-1)/5(2b+1)²
3)4b/(2b-1)-72(2b-1)/5(2b+1)²=
=(80b³+80b²+20b-288b²+288b-72)/5(2b-1)(2b+1)²=
=(80b³-208b²+308b-72)/5(2b-1)(2b+1)²