1.
(y+2)/(y²+y-6)=(y+2)/(y²+3y-2y-6)=(y+2)/((y*(y+3)-2*(y+3))=(y+2)/((y+3)*(y-2))
2.
(y-3)/(y²+5y+6)=(y-3)/(y²+3y+2y+6)=(y-3)/(y*(y+3)+2*(y+3)=(y-3)/((y+3)*(y+2))
3.
(y+2)/((y+3)*(y-2))-(y-3)/(y+3)*(y+2)=((y+2)²-(y-3)*(y-2))/((y+3)*(y-2)*(x+2))=
=(y²+4y+4-y²+5y-6)/((y+3)*(y²-4))=(9y-2)/((y+3)(y²-4))
4.
(y²-4)*(9y-2)/((y+3)*(y²-4)*(2-9y))=-((9y-2)/((x+3)*(9y-2)=-1/(x+3).