Tìm x `x^2-0,81x=0`

#andy

\[\begin{array}{l}
{x^2} - 0,81x = 0\\
 \Rightarrow x\left( {x - 0,81} \right) = 0\\
 \Rightarrow \left[ \begin{array}{l}
x = 0\\
x - 0,81 = 0
\end{array} \right. \Rightarrow \left[ \begin{array}{l}
x = 0\\
x =  - 0,81
\end{array} \right.
\end{array}\]