4 tháng 2 lúc 8:42
\(A=\dfrac{-3}{17}+\left(\dfrac{2}{3}+\dfrac{3}{17}\right)\)
\(=\left(\dfrac{-3}{17}+\dfrac{3}{17}\right)+\dfrac{2}{3}\)
\(=\dfrac{2}{3}\)
\(---\)
\(B=\left(\dfrac{-1}{6}+\dfrac{5}{12}\right)+\dfrac{7}{12}\)
\(=\dfrac{-1}{6}+\left(\dfrac{5}{12}+\dfrac{7}{12}\right)\)
\(=\dfrac{-1}{6}+1\)
\(=\dfrac{-1}{6}+\dfrac{6}{6}=\dfrac{5}{6}\)
\(---\)
\(C=-\dfrac{5}{7}+\dfrac{3}{4}+\dfrac{-1}{5}+\dfrac{-2}{7}+\dfrac{1}{4}\)
\(=\left(\dfrac{-5}{7}+\dfrac{-2}{7}\right)+\left(\dfrac{3}{4}+\dfrac{1}{4}\right)+\dfrac{-1}{5}\)
\(=\left(-1\right)+1-\dfrac{1}{5}\)
\(=-\dfrac{1}{5}\)
\(\text{#}Toru\)
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