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a)
\(\dfrac{4}{9}+\dfrac{2}{9}-\dfrac{5}{18}\\ =\dfrac{6}{9}-\dfrac{5}{18}\\ =\dfrac{6\times2}{9\times2}-\dfrac{5}{18}\\ =\dfrac{12}{18}-\dfrac{5}{18}\\ =\dfrac{7}{18}\)
b)
\(2-\dfrac{3}{5}+\dfrac{8}{15}\\ =\dfrac{2\times15}{15}-\dfrac{3\times3}{5\times3}+\dfrac{8}{15}\\ =\dfrac{30-9+8}{15}\\ =\dfrac{29}{15}\)
c)
\(\dfrac{9}{8}-\left(\dfrac{11}{8}-\dfrac{19}{32}\right)\\ =\dfrac{9}{8}-\left(\dfrac{11\times4}{8\times4}-\dfrac{19}{32}\right)\\ =\dfrac{9}{8}-\left(\dfrac{44}{32}-\dfrac{19}{32}\right)\\ =\dfrac{9}{8}-\dfrac{25}{32}\\ =\dfrac{9\times4}{8\times4}-\dfrac{25}{32}\\ =\dfrac{36-25}{32}\\ =\dfrac{11}{32}\)
a) \(\dfrac{4}{9}+\dfrac{2}{9}-\dfrac{5}{18}=\dfrac{8}{18}+\dfrac{4}{18}-\dfrac{5}{18}=\dfrac{8+4-5}{18}=\dfrac{7}{18}\)
b) \(2-\dfrac{3}{5}+\dfrac{8}{15}=\dfrac{30}{15}-\dfrac{9}{15}+\dfrac{8}{15}=\dfrac{30-9+8}{15}=\dfrac{29}{15}\)
c) \(\dfrac{9}{8}-\left(\dfrac{11}{8}-\dfrac{19}{32}\right)=9-\left(\dfrac{44}{32}-\dfrac{19}{32}\right)=9-\dfrac{25}{32}=\dfrac{288}{32}-\dfrac{25}{32}=\dfrac{288-25}{32}=\dfrac{263}{32}\)
câu a bằng 15/8
câu b bằng 19/6
câu c bằng 3/10
câu d bằng 27/4
5/6 + 9/12 : 18/5 = 5/6 + 3/4 : 18/5
= 5/6 + 3/4 x 5/18
= 5/6 + 15/72
= 5/6 + 5/24
= 20/24 + 5/24
= 25/24
5/7 + 9/8 - 15/28 = 40/56 + 63/56 - 30/56
= 103/56 - 30/56
= 73/56
\(\dfrac{5}{6}+\dfrac{9}{12}:\dfrac{18}{5}\)
\(=\dfrac{5}{6}+\dfrac{5}{24}\)
\(=\dfrac{25}{24}\)
\(---\)
\(\dfrac{5}{7}+\dfrac{9}{8}-\dfrac{15}{28}\)
\(=\dfrac{103}{56}-\dfrac{15}{28}\)
\(=\dfrac{73}{56}\)
5/9 : 4 + 11/18 = 5/9 * 1/4 + 11/18
= 5/36 + 11/18
= 3/4
Đáp án A