Tìm x biết : a, | x| + $\frac{3}{2}$ = 4 b, |3 – x| + $\frac{1}{2}$ = 5 02/07/2021 Bởi Maria Tìm x biết : a, | x| + $\frac{3}{2}$ = 4 b, |3 – x| + $\frac{1}{2}$ = 5
Đáp án: $\\$ `a,` `|x| + 3/2 = 4` `↔ |x| = 4 – 3/2` `↔ |x| = 8/2 – 3/2` `↔ |x| = 5/2` `↔` \(\left[ \begin{array}{l}x=\dfrac{5}{2}\\x=\dfrac{-5}{2}\end{array} \right.\) Vậy `x=5/2` hoặc `x=(-5)/2` $\\$ `b,` `|3 – x| + 1/2 = 5` `↔ |3 – x| = 5 – 1/2` `↔ |3 – x| = 10/2- 1/2` `↔ |3 – x| = 9/2` `↔` \(\left[ \begin{array}{l}3-x=\dfrac{9}{2}\\3-x=\dfrac{-9}{2}\end{array} \right.\) `↔` \(\left[ \begin{array}{l}x=3-\dfrac{9}{2}\\x=3-\dfrac{-9}{2}\end{array} \right.\) `↔` \(\left[ \begin{array}{l}x=\dfrac{6}{2}-\dfrac{9}{2}\\x=\dfrac{6}{2}-\dfrac{-9}{2}\end{array} \right.\) `↔` \(\left[ \begin{array}{l}x=\dfrac{-3}{2}\\x=\dfrac{15}{2}\end{array} \right.\) Vậy `x=(-3)/2` hoặc `x=15/2` Bình luận
Đáp án:
$\\$
`a,`
`|x| + 3/2 = 4`
`↔ |x| = 4 – 3/2`
`↔ |x| = 8/2 – 3/2`
`↔ |x| = 5/2`
`↔` \(\left[ \begin{array}{l}x=\dfrac{5}{2}\\x=\dfrac{-5}{2}\end{array} \right.\)
Vậy `x=5/2` hoặc `x=(-5)/2`
$\\$
`b,`
`|3 – x| + 1/2 = 5`
`↔ |3 – x| = 5 – 1/2`
`↔ |3 – x| = 10/2- 1/2`
`↔ |3 – x| = 9/2`
`↔` \(\left[ \begin{array}{l}3-x=\dfrac{9}{2}\\3-x=\dfrac{-9}{2}\end{array} \right.\)
`↔` \(\left[ \begin{array}{l}x=3-\dfrac{9}{2}\\x=3-\dfrac{-9}{2}\end{array} \right.\)
`↔` \(\left[ \begin{array}{l}x=\dfrac{6}{2}-\dfrac{9}{2}\\x=\dfrac{6}{2}-\dfrac{-9}{2}\end{array} \right.\)
`↔` \(\left[ \begin{array}{l}x=\dfrac{-3}{2}\\x=\dfrac{15}{2}\end{array} \right.\)
Vậy `x=(-3)/2` hoặc `x=15/2`
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