Question

Tìm \(x\in Z,biết:\)

`x(5-x)`\(\ge0\)

Answer 1

Ta có: \(x\left(5-x\right)\ge0\)

+) TH1: \(\left\{{}\begin{matrix}x>0\\5-x>0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x>0\\x< 5\end{matrix}\right.\Rightarrow0< x< 5\)

Mà \(x\in\mathbb{Z}\) nên: \(x\in\left\{1;2;3;4\right\}\) (nhận)

+) TH2: \(\left[{}\begin{matrix}x=0\\5-x=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=5\end{matrix}\right.\left(nhận\right)\)

+) TH3: \(\left\{{}\begin{matrix}x< 0\\5-x< 0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x< 0\\x>5\end{matrix}\right.\left(vô.lí\right)\)

=> loại

Vậy: ...