tính hợp lý:
\(\frac{-4}{13}\). \(\frac{5}{17}\)+ \(\frac{-12}{13}\). \(\frac{4}{17}\)+ \(\frac{4}{13}\)
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\(\frac{-4}{13}.\frac{5}{17}+\frac{-12}{13}.\frac{4}{17}+\frac{4}{13}\)
\(=\frac{4}{13}.\frac{-5}{17}+\frac{-12}{17}.\frac{4}{13}+\frac{4}{13}\)
\(=\frac{4}{13}.\left(\frac{-5}{17}+\frac{-12}{17}+1\right)\)
\(=\frac{4}{13}.0\)
\(=0\)
\(=\frac{9}{16}.\left(\frac{13}{4}+\frac{17}{4}\right)-\frac{9}{4}.\frac{5}{16}\)
\(=\frac{9}{16}.\frac{30}{4}-\frac{9}{4}.\frac{5}{16}\)
\(=\left(\frac{9}{16}-\frac{5}{16}\right).\left(\frac{30}{4}-\frac{9}{4}\right)\)
\(=\frac{1}{4}.\frac{21}{4}=\frac{21}{16}\)
Hok tốt~
Trả lời
\(\frac{31}{17}+\left(\frac{-5}{13}\right)+\left(\frac{-8}{13}\right)-\frac{4}{17}\)
\(=\left(\frac{31}{17}-\frac{4}{17}\right)+\left[\left(\frac{-5}{13}\right)+\left(\frac{-8}{13}\right)\right]\)
\(=\frac{27}{17}+\left(\frac{-13}{13}\right)\)
\(=\frac{27}{17}+\left(-1\right)\)
\(=\frac{10}{17}\)
\(\frac{31}{17}+\frac{-5}{13}+\frac{-8}{13}-\frac{4}{17}\)
\(=\left(\frac{31}{17}-\frac{4}{17}\right)+\left(\frac{-5}{13}+\frac{-8}{13}\right)\)
\(=\frac{27}{13}+\frac{-13}{13}\)
\(=\frac{27}{13}+\left(-1\right)\)
\(=\frac{10}{17}\)
\(\left(\frac{-4}{13}+\frac{4}{13}+\frac{-12}{13}\right)\times\left(\frac{5}{17}+\frac{4}{17}\right)\)
\(=\)\(\frac{-12}{13}\times\left(\frac{5}{17}+\frac{4}{17}\right)\)
\(=\)\(\frac{-12}{13}\times\frac{9}{17}=\frac{-106}{221}\)
\(B=\frac{3+\frac{8}{12}+\frac{9}{13}-\frac{12}{17}}{4+\frac{8}{12}+\frac{12}{13}-\frac{16}{17}}+\frac{4+\frac{16}{60}-\frac{24}{213}-\frac{32}{11}}{5+\frac{20}{61}-\frac{36}{213}-\frac{40}{11}}\)
\(\Leftrightarrow B=\frac{3\left(1+\frac{8}{12}+\frac{3}{13}-\frac{4}{17}\right)}{4\left(1+\frac{8}{12}+\frac{3}{13}-\frac{4}{17}\right)}+\frac{4\left(1+\frac{4}{60}-\frac{6}{213}-\frac{8}{11}\right)}{5\left(1+\frac{4}{60}+\frac{6}{213}-\frac{8}{11}\right)}\)
\(\Leftrightarrow B=\frac{3}{4}+\frac{4}{5}\)
\(\Leftrightarrow B=\frac{15}{20}+\frac{16}{20}\)
\(\Leftrightarrow B=\frac{31}{20}\)
a)\(\frac{-10}{13}+\frac{8}{17}-\frac{3}{13}+\frac{12}{17}-\frac{11}{20}\)
= \(\frac{-10}{13}+\frac{8}{17}+\frac{-3}{13}+\frac{12}{17}+\frac{-11}{20}\)
=\(\left(\frac{-10}{13}+\frac{-3}{13}\right)+\left(\frac{8}{17}+\frac{12}{17}\right)+\frac{-11}{20}\)
=\(\frac{-13}{13}+\frac{20}{17}+\frac{-11}{20}\)
= \(\frac{-127}{340}\)
b) \(\frac{3}{4}+\frac{-5}{6}-\frac{11}{-12}\)
= \(\frac{3}{4}+\frac{-5}{6}+\frac{11}{12}\)
= \(\frac{9}{12}+\frac{-10}{12}+\frac{11}{12}\)
=\(\frac{10}{12}=\frac{5}{6}\)
c) \(\left[13.\frac{4}{9}+2.\frac{1}{9}\right]-3.\frac{4}{9}\)
= \(13+2.\left(\frac{4}{9}+\frac{1}{9}\right)-3.\frac{4}{9}\)
=\(15.\frac{5}{9}-3.\frac{4}{9}\)
=\(\left[15-3.\left(\frac{5}{9}-\frac{4}{9}\right)\right]\)
=\(12.\frac{1}{9}\)
=\(\frac{4}{3}\)
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