Giải thích các bước giải:
\(\begin{array}{l}
2,\\
a,\\
\frac{{ - 9x{y^5}}}{{12{x^2}{y^3}}} = \frac{{3x{y^3}.\left( { - 3{y^2}} \right)}}{{3x{y^3}.4x}} = \frac{{ - 3{y^2}}}{{4x}}\\
b,\\
\frac{{{x^2} + 2x + 1}}{{2x + 2}} = \frac{{{{\left( {x + 1} \right)}^2}}}{{2\left( {x + 1} \right)}} = \frac{{x + 1}}{2}\\
3,\\
a,\\
\frac{{2x + 3}}{{x - 3}} + \frac{{x - 12}}{{x - 3}} = \frac{{2x + 3 + x - 12}}{{x - 3}} = \frac{{3x - 9}}{{x - 3}} = \frac{{3\left( {x - 3} \right)}}{{x - 3}} = 3\\
b,\\
\frac{{4{x^2} - 1}}{{2{x^2} + x}}:\frac{{3 - 6x}}{{4x}} = \frac{{\left( {2x - 1} \right)\left( {2x + 1} \right)}}{{x\left( {2x + 1} \right)}}.\frac{{4x}}{{3\left( {1 - 2x} \right)}} = - \frac{4}{3}
\end{array}\)
