Rút gọn biểu thức:\(\begin{align}  & a)\frac{1...

Câu hỏi: Rút gọn biểu thức:\(\begin{align}  & a)\frac{1}{x+2}+\frac{1}{(x+1)(x+2)}+\frac{1}{(x+1)(2x+1)} \\& b)\frac{4{{x}^{2}}-3x+5}{{{x}^{3}}-1}-\frac{1-2x}{{{x}^{2}}+x+1}-\frac{6}{x-1} \\ \end{align}\)

A \(\begin{array}{l}
a)\,\,\,-\frac{2}{{2x + 1}}\\
b)\,\,\frac{{  12x}}{{{x^3} - 1}}
\end{array}\)

B \(\begin{array}{l}
a)\,\,\,-\frac{2}{{2x + 1}}\\
b)\,\,\frac{{ - 12x}}{{{x^3} - 1}}
\end{array}\)

C \(\begin{array}{l}
a)\,\,\,\frac{2}{{2x + 1}}\\
b)\,\,\frac{{ - 12x}}{{{x^3} - 1}}
\end{array}\)

D \(\begin{array}{l}
a)\,\,\,\frac{2}{{2x + 1}}\\
b)\,\,\frac{{ 12x}}{{{x^3} - 1}}
\end{array}\)