\(pt\Leftrightarrow8m^2-18m-18=0\)
\(\Leftrightarrow8m^2+6m-24m-18=0\)
\(\Leftrightarrow2m\left(4m+3\right)-6\left(4m+3\right)=0\)
\(\Leftrightarrow\left(4m+3\right)\left(2m-6\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}4m+3=0\\2m-6=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}m=-\dfrac{3}{4}\\m=3\end{matrix}\right.\)
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