Question

(x^2-9)(-2x+8)=0

Answer 1

\(\left(x^2-9\right)\left(-2x+8\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x^2-9=0\\-2x+8=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x^2=9\\-2x=-8\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\pm3\\x=4\end{matrix}\right.\)

\(S=\left\{\pm3,4\right\}\)

Answer 2

       (x² - 9)(-2x + 8) = 0

<=>  (x - 3) (x + 3) (-2x + 8) = 0

<=.  \(\left[{}\begin{matrix}x-3=0\\x+3=0\\\text{-2x + 8 = 0}\end{matrix}\right.\)  <=> \(\left[{}\begin{matrix}x-3=0\\x+3=0\\\text{-2x + 8 = 0}\end{matrix}\right.\)     <=> \(\left[{}\begin{matrix}x=3\\x=-3\\\text{​​}x=4\end{matrix}\right.\)

Vậy x \(\in\left\{3;-3;4\right\}\)