Bài `2:`
`a,|x|=2,45`
`↔` \(\left[ \begin{array}{l}x=2,45\\x=-2,45\end{array} \right.\)
Vậy `x\in{2,45;-2,45}`
`b,|2x|=7,5`
`↔` \(\left[ \begin{array}{l}2x=7,5\\2x=-7,5\end{array} \right.\)
`↔` \(\left[ \begin{array}{l}x=3,75\\x=-3,75\end{array} \right.\)
Vậy `x\in{3,75;-3,75}`
`c,|-3x|=9`
`↔` \(\left[ \begin{array}{l}-3x=9\\-3x=-9\end{array} \right.\)
`↔` \(\left[ \begin{array}{l}x=3\\x=-3\end{array} \right.\)
Vậy `x\in{3;-3}`
`d,|-5x|=-20`
Do `|-5x|>=0` mà `-20<0` nên:
`→x\in∅`
Vậy `x\in∅`
`e,|x-1|=5,45`
`↔` \(\left[ \begin{array}{l}x-1=5,45\\x-1=-5,45\end{array} \right.\)
`↔` \(\left[ \begin{array}{l}x=6,45\\x=-4,45\end{array} \right.\)
Vậy `x\in{6,45;-4,45}`
`f,|x+3/2|=1/2`
`↔` \(\left[ \begin{array}{l}x+\dfrac{3}{2}=\dfrac{1}{2}\\x+\dfrac{3}{2}=-\dfrac{1}{2}\end{array} \right.\)
`↔` \(\left[ \begin{array}{l}x=-1\\x=-2\end{array} \right.\)
Vậy `x\in{-1;-2}`
`g,|3x-1/2|=13/2`
`↔` \(\left[ \begin{array}{l}3x-\dfrac{1}{2}=\dfrac{13}{2}\\3x-\dfrac{1}{2}=-\dfrac{13}{2}\end{array} \right.\)
`↔` \(\left[ \begin{array}{l}3x=7\\3x=-6\end{array} \right.\)
`↔` \(\left[ \begin{array}{l}x=\dfrac{7}{3}\\x=-2\end{array} \right.\)
Vậy `x\in{7/3;-2}`
`h,|5x+1/2|=-15/4`
Do `|5x+1/2|>=0` mà `-15/4<0` nên:
`→x\in∅`
Vậy `x\in∅`
