Question

tìm y để \(4y-2y^2\ge0\)

Answer 1

Lời giải:

\(4y-2y^2\geq 0\)

\(\Leftrightarrow 2y(2-y)\geq 0\)

\(\Leftrightarrow y(2-y)\geq 0\)

\(\Leftrightarrow \left\{\begin{matrix} y\geq 0\\ 2-y\geq 0\end{matrix}\right.\) hoặc \(\Leftrightarrow \left\{\begin{matrix} y\leq 0\\ 2-y\leq 0\end{matrix}\right.\)

\(\Leftrightarrow \left\{\begin{matrix} y\geq 0\\ y\leq 2\end{matrix}\right.\) hoặc \(\left\{\begin{matrix} y\leq 0\\ y\geq 2\end{matrix}\right.\) (vô lý)

Vậy \(\left\{\begin{matrix} y\geq 0\\ y\leq 2\end{matrix}\right.\)