a. \(\frac{\left(2x^2+3x^2\right)\left(2x+1\right)}{4x^3-9x}=\frac{x^2.\left(2x+3\right)\left(2x+1\right)}{x\left(4x^2-9\right)}\)
\(=\frac{x^2\left(2x+3\right)\left(2x+1\right)}{x\left(2x+3\right)\left(2x-3\right)}=\frac{x\left(2x+1\right)}{2x-3}\)
b,Để \(P=0\rightarrow\frac{x\left(2x+1\right)}{2x-3}=0\)
\(\rightarrow x\left(2x+1\right)=0\)
\(\rightarrow\left[{}\begin{matrix}x=0\\2x+1=0\end{matrix}\right.\)
\(\rightarrow\left[{}\begin{matrix}x=0\\x=\frac{-1}{2}\end{matrix}\right.\)