Giúp mình với ạ, mình xin cảm ơn trước ạ !.
\(\dfrac{5}{21}\) + \(\dfrac{1}{2}\) - \(\dfrac{19}{23}\) + \(\dfrac{16}{21}\) - \(\dfrac{4}{23}\)
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\(1\dfrac{4}{23}+\left(\dfrac{5}{21}-\dfrac{4}{23}\right)+\dfrac{16}{21}-\dfrac{1}{2}\)
\(=1\dfrac{4}{23}-\dfrac{4}{23}+\dfrac{5}{21}+\dfrac{16}{21}+\dfrac{1}{2}\)
\(=1+1-\dfrac{1}{2}\)
\(=\dfrac{3}{2}\)
1 4/23 + ( 5/21-4/23 ) + 16/21 - 1/2
=1 4/23 - 4/23 + 5/21 + 16/21 + 1/2
= 1+1-1/2
=3/2
\(\dfrac{27}{23}\) + \(\dfrac{5}{21}\) - \(\dfrac{4}{23}\) + \(0,5\) + \(\dfrac{16}{21}\)
= [ \(\dfrac{27}{23}\) - \(\dfrac{4}{23}\) ] + [ \(\dfrac{5}{21}\) + \(\dfrac{16}{21}\) ] + 0,5
= 1 + 1 + 0,5
= 2 + 0,5
= 2,5
\(a,\dfrac{3}{5}+\dfrac{-5}{9}=\dfrac{27-25}{45}=\dfrac{2}{49}.\)
\(c,\dfrac{-27}{23}+\dfrac{5}{21}+\dfrac{4}{23}+\dfrac{16}{21}+\dfrac{1}{2}=\dfrac{-23}{23}+\dfrac{21}{21}+\dfrac{1}{2}=-1+1+\dfrac{1}{2}=\dfrac{1}{2}.\)
\(d,\dfrac{-8}{9}+\dfrac{1}{9}.\dfrac{2}{9}+\dfrac{1}{9}.\dfrac{7}{9}=\dfrac{-8}{9}+\dfrac{1}{9}.\left(\dfrac{2}{9}+\dfrac{7}{9}\right)=\dfrac{-8}{9}+\dfrac{1}{9}.1=\dfrac{-8+1}{9}=\dfrac{-7}{9}.\)
\(\left(1\dfrac{4}{23}-\dfrac{5}{21}\right)-\left(\dfrac{4}{23}-\dfrac{3}{4}\right)-\dfrac{16}{21}\)
\(=\left(1\dfrac{4}{23}-\dfrac{4}{23}\right)-\left(\dfrac{5}{21}+\dfrac{16}{21}\right)+\dfrac{3}{4}=1-1+\dfrac{3}{4}=\dfrac{3}{4}\)
\(=\dfrac{5}{21}+\dfrac{16}{21}-\left(\dfrac{19}{23}+\dfrac{4}{23}\right)+\dfrac{1}{2}=\dfrac{1}{2}\)