\(\left|x-5\right|-x=19\)
\(\Leftrightarrow\left|x-5\right|=19+x\)
\(\Leftrightarrow\left(\left|x-5\right|\right)^2=\left(x+19\right)^2\)
\(\Leftrightarrow x^2-10x+25=x^2+38x+361\)
\(\Leftrightarrow-48x=336\Leftrightarrow x=-7\) (thỏa mãn)
Bình phương lớp 7 sao hiểu được
(I)\(\left\{{}\begin{matrix}x-5\ge0\Rightarrow x\ge5\\\left|x-5\right|=x-5\\\Leftrightarrow x-5-x=19\Rightarrow-5\ne19VN\end{matrix}\right.\)
(II)\(\left\{{}\begin{matrix}x-5< 0\Rightarrow x< 5\\\left|x-5\right|=5-x\\\Leftrightarrow5-x-x=19\Rightarrow5-2x=19\Rightarrow x=-7\left(nhan\right)\end{matrix}\right.\)
DS: x=-7
