Б
13c/b(m-n)+12b/c(m-n)=(13c²+12b²)/bc)m-n)
г
(2y+1)/y(y+3)+(y+2)/y(3-y)-1/y=[(3-y)(2y+1)+(y+2)(3+y)-(y+3)(3-y)]/y(9-y²)=
=(6y-2y²+3-y+3y+y²+6+2y-9+y²)/y(9-y²)=(10y+9)/y(9-y²)