Bài 5:
c: \(4x^2-9=0\)
\(\Leftrightarrow\left(2x-3\right)\left(2x+3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=-\dfrac{3}{2}\end{matrix}\right.\)
f: \(x\left(2x+9\right)-4x+18=0\)
\(\Leftrightarrow\left(2x+9\right)\left(x-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{9}{2}\\x=2\end{matrix}\right.\)