b)
D=R-{-3,-1,3}
\frac{x^3+3x^2-x-3}{x^3+x^2-9x-9}=\frac{x^2(x+3)-(x+3)}{x^2(x+1)-9(x+1)}=\frac{(x+3)(x^2-1)}{(x+1)(x^2-9)}=\frac{(x+3)(x-1)(x+1)}{(x+1)(x-3)(x+3)}=\frac{x-1}{x-3}
c)
3x^2-5x-2
\Delta=25+24=49
\sqrt\Delta=7
x_1=\frac{5-7}{6}=-\frac{1}{3}
x_2=\frac{5+7}{6}=2
\frac{3x+1}{3(x+\frac{1}{3})(x-2)}=\frac{3x+1}{(3x+1)(x-2)}=\frac{1}{x-2}