bài 1: tìm x biết:
1) \(\left|x\right|< 4\)
2)\(\left|x+21\right|>7\)
3)\(\left|x-1\right|< 3\)
4)\(\left|x+1\right|>2\)
bài 2:tìm x,y biết:
\(\left|x+\frac{1}{2}\right|+\left|3-y\right|=0\)
bài 4 tìm x biết:
1)\(\left|x-5\right|=5-x\)
2)\(\left|x-7\right|=7-x\)
3)\(\left|x+5,9\right|=3.x\)
4)\(\left|4,03-x\right|=5.x\)
5)\(\left|x-9\right|=x-9\)
giúp mình nha cám ơn các bạn nhiều
1) \(\left|x\right|< 4\Leftrightarrow-4< x< 4\)
2) \(\left|x+21\right|>7\Leftrightarrow\orbr{\begin{cases}x+21>7\\x+21< -7\end{cases}}\Leftrightarrow\orbr{\begin{cases}x>-14\\x< -28\end{cases}}\)
3) \(\left|x-1\right|< 3\Leftrightarrow-3< x-1< 3\Leftrightarrow-2< x< 4\)
4) \(\left|x+1\right|>2\Leftrightarrow\orbr{\begin{cases}x+1>2\\x+1< -2\end{cases}}\Leftrightarrow\orbr{\begin{cases}x>1\\x< -3\end{cases}}\)
\(\left|x+\frac{1}{2}\right|+\left|3-y\right|=0\)
Vì \(\hept{\begin{cases}\left|x+\frac{1}{2}\right|\ge0\\\left|3-y\right|\ge0\end{cases}}\Rightarrow\)\(\left|x+\frac{1}{2}\right|+\left|3-y\right|\ge0\)
Dấu "="\(\Leftrightarrow\hept{\begin{cases}\left|x+\frac{1}{2}\right|=0\\\left|3-y\right|=0\end{cases}}\Leftrightarrow\hept{\begin{cases}x=\frac{-1}{2}\\y=3\end{cases}}\)