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\(\dfrac{-3}{16};\dfrac{-21}{56}\) MSC : 112
\(\dfrac{-3}{16}=\dfrac{\left(-3\right)\cdot7}{16\cdot7}=\dfrac{-21}{112}\)
\(\dfrac{-21}{56}=\dfrac{\left(-21\right)\cdot2}{56\cdot2}=\dfrac{-42}{112}\)
Vậy \(\dfrac{-3}{16};\dfrac{-21}{56}\) quy đồng lên ta được 2 phân số : \(\dfrac{-21}{112};\dfrac{-42}{112}\)
a, \(\frac{3}{8};-\frac{7}{11}\)
Quy đồng mẫu số: \(\frac{3}{8}=\frac{3\cdot11}{8\cdot11}=\frac{33}{88};-\frac{7}{11}=\frac{-7\cdot8}{11\cdot8}=-\frac{56}{88}\)
b, \(\frac{7}{15};-6\)
Quy đồng mẫu số: \(-6=\frac{-6\cdot15}{15}=-\frac{90}{15}\)
c, \(-\frac{3}{16};\frac{-5}{-24}\) ; \(-\frac{21}{56}\)
Quy đồng mẫu số:
\(-\frac{3}{16}=\frac{-3\cdot3}{16\cdot3}=-\frac{9}{48};\frac{-5}{-24}=\frac{5}{24}=\frac{5\cdot2}{24\cdot2}=\frac{10}{48}\)
\(-\frac{21}{56}=-\frac{3}{8}=\frac{-3\cdot6}{8\cdot6}=-\frac{18}{48}\)
Lời giải:
$\frac{-3}{16}=\frac{-3.21}{16.21}=\frac{-63}{336}$
$\frac{5}{24}=\frac{5.14}{24.14}=\frac{70}{336}$
$\frac{-21}{56}=\frac{-21.6}{56.6}=\frac{-126}{336}$
\(\dfrac{-3}{16};\dfrac{5}{24};\dfrac{-21}{56}\) MSC : 336
\(\dfrac{-3}{16}=\dfrac{\left(-3\cdot21\right)}{16\cdot21}=\dfrac{-63}{336}\)
\(\dfrac{5}{24}=\dfrac{5\cdot14}{24\cdot14}=\dfrac{70}{336}\)
\(\dfrac{-21}{56}=\dfrac{\left(-21\cdot6\right)}{56\cdot6}=\dfrac{-126}{336}\)
\(\frac{7}{8}\div\left(\frac{14}{3}+\frac{14}{4}\right)+\frac{10}{14}\)
\(=\frac{7}{8}\div\left(\frac{56}{12}+\frac{52}{12}\right)+\frac{10}{14}\)
\(=\frac{7}{8}\div\frac{108}{12}+\frac{10}{14}\)
\(=\frac{7}{8}\div9+\frac{5}{7}\)
\(=\frac{7}{8}\times\frac{1}{9}+\frac{5}{7}\)
\(=\frac{7}{72}+\frac{5}{7}\)
\(=\frac{49}{504}+\frac{360}{504}\)
\(=\frac{409}{504}\)
\(\frac{30}{42}\div\left(\frac{5}{7}-\frac{5}{21}\right)+\frac{6}{8}\)
\(=\frac{6}{7}\div\left(\frac{15}{21}-\frac{5}{21}\right)+\frac{3}{4}\)
\(=\frac{6}{7}\div\frac{10}{21}+\frac{3}{4}\)
\(=\frac{6}{7}\times\frac{21}{10}+\frac{3}{4}\)
\(=\frac{126}{70}+\frac{3}{4}\)
\(=\frac{504}{280}+\frac{210}{280}\)
\(=\frac{714}{280}\)
\(\left(6-\frac{14}{15}\right).\frac{50}{38}-\frac{8}{18}\)
\(=\left(\frac{90}{15}-\frac{14}{15}\right).\frac{25}{19}-\frac{4}{9}\)
\(=\frac{76}{15}.\frac{25}{19}-\frac{4}{9}\)
\(=\frac{76.25}{15.19}-\frac{4}{9}\)
\(=\frac{19.2.2.5.5}{3.5.19}-\frac{4}{9}\)
\(=\frac{20}{3}-\frac{4}{9}\)
\(=\frac{60}{9}-\frac{4}{9}\)
\(=\frac{56}{9}\)
\(\frac{4}{6}+\frac{5}{21}.\left(\frac{4}{5}-\frac{2}{6}\right)\)
\(=\frac{2}{3}+\frac{5}{21}.\left(\frac{24}{30}-\frac{10}{30}\right)\)
\(=\frac{2}{3}+\frac{5}{21}.\frac{14}{30}\)
\(=\frac{2}{3}+\frac{70}{630}\)
\(=\frac{420}{630}+\frac{70}{630}\)
\(=\frac{490}{630}\)
\(=\frac{7}{9}\)
làm cho rồi đó : https://hoc24.vn/cau-hoi/c-316-21-phan-56-quy-dong-a.5608508996971
\(-\dfrac{3}{16}=\dfrac{-3.7}{16.7}=-\dfrac{21}{112}\)
\(-\dfrac{21}{56}=\dfrac{-21.2}{56.2}=-\dfrac{42}{112}\)