Question

Tìm x, biết:

      x²(x-7)-9(x-7)

Answer 1

\(x^2\left(x-7\right)-9\left(x-7\right)=0\)

\(\Rightarrow\left(x+3\right)\left(x-3\right)\left(x-7\right)=0\)

\(\Rightarrow x+3=0\) hoặc \(x-3=0\) hoặc \(x-7=0\)

\(\Rightarrow x\in\left\{-3;3;7\right\}\)

Vậy \(x\in\left\{-3;3;7\right\}\)

Answer 2

\(x^2\left(x-7\right)-9\left(x-7\right)=0\)

\(\Leftrightarrow\left(x-7\right)\left(x^2-9\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x-7=0\\x^2-9=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=7\\x=\pm3\end{cases}}\)

Vậy: ...

Answer 3

Thanks...