| 5-4x| + | 7y-3| = 0
=> | 5 - 4x| = 0 => 5-4x = 0 => 4x = 5 => x = 5/4
|7y-3| = 0 => 7y -3 = 0 => 7y = 3 => y = 3/7
KL: x = 5/4; y = 3/7
\(\left|5-4x\right|+\left|7y-3\right|=0.\)
Nhận xét : \(\hept{\begin{cases}\left|5-4x\right|\ge0\\\left|7y-3\right|\ge0\end{cases}\Rightarrow}\)\(\left|5-4x\right|+\left|7y-3\right|\ge0.\)
Dấu \("="\)xảy ra \(\Leftrightarrow\hept{\begin{cases}\left|5-4x\right|=0\\\left|7y-3\right|=0\end{cases}}\Leftrightarrow\hept{\begin{cases}5-4x=0\\7y-3=0\end{cases}\Leftrightarrow\hept{\begin{cases}4x=5\\7y=3\end{cases}\Leftrightarrow}\hept{\begin{cases}x=\frac{5}{4}\\y=\frac{3}{7}\end{cases}}}\)
Vậy : \(\begin{cases}x=\frac{5}{4}\\y=\frac{3}{7}\end{cases}\)
Nhãn
