a) $\frac{x^2+2x+1}{x-2}\times \frac{2x-4}{2x(x+1)}\\=\frac{2(x+1)^2(x-2)}{2x(x+1)(x-2)}\\=\frac{x+1}{x}$
b) $\frac{-2}{x+3}-\frac{3}{3-x}-\frac{12}{x^2-9}\\=\frac{-2}{x+3}+\frac{3}{x+3}-\frac{12}{(x-3)(x+3)}\\frac{1}{x+3}-\frac{12}{(x-3)(x+3)}\\=\frac{x+9}{(x-3)(x+3)}$
