\(x^2-5x-14=0\)
\(\Leftrightarrow x^2+2x-7x-14=0\)
\(\Leftrightarrow x\left(x+2\right)-7\left(x+2\right)=0\)
\(\Leftrightarrow\left(x+2\right)\left(x-7\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x+2=0\\x-7=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=7\end{matrix}\right.\)
Vậy: \(S=\left\{-2;7\right\}\)
\(x^2-5x-14=0\)
=>\(x^2-7x+2x-14=0\)
=>\(\left(x-7\right)\left(x+2\right)=0\)
=>\(\left[{}\begin{matrix}x-7=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=7\\x=-2\end{matrix}\right.\)
`x^2 -5x-14=0`
`<=>x^2 +2x-7x-14=0`
`<=> (x^2 +2x)-(7x+14)=0`
`<=> x (x+2)-7(x+2)=0`
`<=>(x+2)(x-7)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x+2=0\\x-7=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=-2\\x=7\end{matrix}\right.\)
