Lời giải:
1.
a) `|x- 1/3| = 1/5`
\(\left[ \begin{array}{l}x-\dfrac{1}{3}=\dfrac{1}{5}\\x-\dfrac{1}{3}=-\dfrac{1}{5}\end{array} \right.\)
\(\left[ \begin{array}{l}x=\dfrac{8}{15}\\x=\dfrac{2}{15}\end{array} \right.\)
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`x= -1/2 + 1/3 - |-1/7|`
`x=-1/2+1/3 - (-1/7)`
`x=-1/6-(1/7)`
`x=-13/42`
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2. So sánh:
a) `-53/54` và `-54/55`
`-53/54=1/54 - 1`
`-54/55=1/55-1`
Ta so sánh phần bù:
`1/54>1/55=>1/54-1 > 1/55-1`
`=>-53/54>-54/55`
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b)
$A=\dfrac{10^{20}+1 }{10^{21}}=1$
$B=\dfrac{10^{21}+1 }{10^{22}}=1$
`=>` $\dfrac{10^{20}+1 }{10^{21}} = \dfrac{10^{21}+1 }{10^{22}}$