a,Ta có:
\(x^3-9x=0\Rightarrow x.\left(x^2-9\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x^2-9=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x^2=9\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=\pm3\end{matrix}\right.\)
Vậy...........
b,Ta có:
\(x^2+5x-6=0\)
\(\Rightarrow x^2+x-6x-6=0\)
\(\Rightarrow x.\left(x+1\right)-6.\left(x+1\right)=0\)
\(\Rightarrow\left(x+1\right).\left(x-6\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x+1=0\\x-6=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-1\\x=6\end{matrix}\right.\)
Vậy........
Chúc bạn học tốt!!!
\(x^3-9x=0\)
\(\Rightarrow x\left(x^2-9\right)=0\)
\(\Rightarrow x=0\)
\(\Rightarrow x^2-9=0\Rightarrow x^2=9\Rightarrow x=3\)
\(x^2+5x+6=0\)
\(x^2+2x+3x+6=0\)
\(x\left(x+2\right)+3\left(x+2\right)=0\)
\(\left(x+3\right)\left(x+2\right)=0\)
\(\Rightarrow x+3=0\Rightarrow x=-3\)
\(\Rightarrow x+2=0\Rightarrow x=-2\)