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Mẫu 21:
\(\dfrac{4}{7}=\dfrac{4x3}{7x3}=\dfrac{12}{21}\)
Mẫu 35:
\(\dfrac{4}{7}=\dfrac{4x5}{7x5}=\dfrac{20}{35}\)
Mẫu 49:
\(\dfrac{4}{7}=\dfrac{4x7}{7x7}=\dfrac{28}{49}\)
Ba phân số đó là:1/16;1/8 và 1/4.Ko cần cảm ơn, chỉ cần k thôi!
Ta có:\(\frac{7}{16}=\frac{1}{16}+\frac{2}{16}+\frac{4}{16}=\frac{1}{16}+\frac{1}{8}+\frac{1}{4}\)
Vậy A viết dưới dạng tổng của 3 phân số:\(\frac{1}{16},\frac{1}{8},\frac{1}{4}\)
\(\dfrac{11}{16}\) = \(\dfrac{1}{16}\) + \(\dfrac{10}{16}\) = \(\dfrac{1}{16}\) + \(\dfrac{2+8}{2\times8}\) = \(\dfrac{1}{16}\) + \(\dfrac{2}{2\times8}\) + \(\dfrac{8}{2\times8}\) = \(\dfrac{1}{16}\) + \(\dfrac{1}{8}\)+ \(\dfrac{1}{2}\)
\(\dfrac{5}{12}\) = \(\dfrac{1}{12}\) + \(\dfrac{4}{12}\) = \(\dfrac{1}{12}\) + \(\dfrac{4}{3\times4}\) = \(\dfrac{1}{12}\) + \(\dfrac{1}{3}\)
Ta có: \(\frac{3}{9}=\frac{3\cdot2}{9\cdot2}=\frac{6}{18}\)
Mà \(\frac{6}{18}=\frac{1}{18}+\frac{2}{18}+\frac{3}{18}\)
\(=\frac{1}{18}+\frac{1}{9}+\frac{1}{6}\)
\(\Rightarrow\frac{3}{9}=\frac{1}{18}+\frac{1}{9}+\frac{1}{6}\)
\(\dfrac{7}{12}=\dfrac{1}{2}+\dfrac{1}{12}\\ \dfrac{9}{12}=\dfrac{3}{4}=\dfrac{1}{2}+\dfrac{1}{4}\)
\(\dfrac{7}{12}\) = \(\dfrac{3+4}{12}\) = \(\dfrac{3}{12}\) + \(\dfrac{4}{12}\) = \(\dfrac{1}{4}\) + \(\dfrac{1}{3}\)
\(\dfrac{7}{12}\) = \(\dfrac{1+6}{12}\) = \(\dfrac{1}{12}\) + \(\dfrac{6}{12}\) = \(\dfrac{1}{12}\) + \(\dfrac{1}{2}\)
\(\dfrac{9}{12}\) = \(\dfrac{3+6}{12}\) = \(\dfrac{3}{12}\) + \(\dfrac{6}{12}\) = \(\dfrac{1}{4}\) + \(\dfrac{1}{2}\)