1) (x+2)/(x+3) - (x-1)/x =(x(x+2) -(x+3)(x-1))/(x(x-1)) =
(x² +2x -x² +x -3x+3)/(x(x-1)) =3/(x(x-1)) .
2) (a³ +3)/a³ -(3-a)/3a = 1+3/a³ -1/a+1/3=4/3 +(3-a²)/a³.
или по другому :
( 3(a³+3) -(3-a)a² )/3a³ =(3a³ +9 -3a²+a³)/3a³ =(4a³ +3(3-a²))/3a³ =4/3 + (3-a²))/a³.
3) 18x³/(7*b^4 )*14b/9x² = (18x³ *14b)/(7*(b^4)*9x²)= 2x/b³.