Ответ: (4-b)(c+a)
Объяснение: 4с-сb+4a-ab = c(4-b)+a(4-b)=(4-b)(c+a)
((y+1)/(y-1)-y/(y+1))*(3y+1)/(y²+y)=((y+1)²-(y²-y)/(y²-1))*(3y+1)/(y²+y)=
=((y²+2y+1-y²+y)/(y²-1))*(3y+1)/(y²+y)=((3y+1)/(y²-1))*(3y+1)/(y²+y)=
=(3y+1)²/((y-1)(y+1)*y*(y+1))=(3y+1)²/(y*(y+1)²*(y-1)).