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\(=\frac{16}{5}.\frac{15}{16}-\left(\frac{3}{4}+\frac{2}{7}\right):\left(\frac{-29}{28}\right)\)
\(=3-\left(\frac{21}{28}+\frac{8}{28}\right):\left(\frac{-29}{28}\right)\)
\(=3-\left(\frac{29}{28}\right).\left(\frac{-28}{29}\right)\)
\(=3-\left(-1\right)\)
\(=4\)
b) \(=\left(\frac{1}{4}+\frac{25}{2}-\frac{5}{16}\right):\left(12-\frac{7}{12}:\left(\frac{3}{8}-\frac{1}{12}\right)\right)\)
\(=\left(\frac{4}{16}+\frac{200}{16}-\frac{5}{16}\right):\left(12-\frac{7}{12}:\left(\frac{3.3}{2.3.4}-\frac{2}{2.3.4}\right)\right)\)
\(=\left(\frac{199}{16}\right):\left(12-\frac{7}{12}:\left(\frac{9}{24}-\frac{2}{24}\right)\right)\)
\(=\frac{199}{16}:\left(12-\frac{7}{12}.\frac{24}{7}\right)\)
\(=\frac{199}{16}:\left(12-2\right)\)
\(=\frac{199}{16}:10\)
\(=\frac{199}{160}\)
c) \(\left(\frac{-3}{5}+\frac{5}{11}\right):\frac{-3}{7}+\left(\frac{-2}{5}+\frac{6}{5}\right):\frac{-3}{7}\)
\(\left(\frac{-33}{55}+\frac{25}{55}\right):\frac{-3}{7}+\left(\frac{4}{5}\right):\frac{-3}{7}\)
\(\left(\frac{-8}{55}\right).\frac{-7}{3}+\frac{4}{5}.\frac{-7}{3}\)
\(\frac{-7}{3}\left(\frac{-8}{55}+\frac{4}{5}\right)\)
\(\frac{-7}{3}.\frac{36}{55}=\frac{-84}{55}\)
a, 6/7 + (2/11 - 6/7) - (13/11 + 1)
= 6/7 + 2/11 - 6/7 - 13/11 - 1
= (6/7 - 6/7) - (13/11 - 2/11) - 1
= 0 - 1 - 1
= -2
* Vì ko ai trả lời nên mình tự trả lời nhé ! *
F = \(\frac{6}{7}\). \(\left|\frac{5}{8}-\frac{7}{12}\div x\right|-19\)
Dùng KT | x | \(\ge\)0 \(\forall\)x
Bài giải :
Ta có : \(\left|\frac{5}{8}-\frac{7}{12}\div x\right|\)\(\ge\)0 \(\forall\)x ; \(\frac{6}{7}\)> 0
nên : \(\frac{6}{7}\). \(\left|\frac{5}{8}-\frac{7}{12}\div x\right|\)\(\ge\)0 \(\forall\)x
\(\Leftrightarrow\)\(\frac{6}{7}\). \(\left|\frac{5}{8}-\frac{7}{12}\div x\right|-19\)\(\ge\)0 - 19 \(\forall\)x
Hay F \(\ge\)- 19 \(\forall\)x
Dấu " = " xảy ra khi : \(\Leftrightarrow\)\(\left|\frac{5}{8}-\frac{7}{12}\div x\right|=0\)
\(\Leftrightarrow\)\(\frac{5}{8}-\frac{7}{12}\div x=0\)
\(\Leftrightarrow\)\(\frac{7}{12}\div x=\frac{5}{8}\)\(\Leftrightarrow\)\(x=\frac{7}{12}\div\frac{5}{8}\)\(\Leftrightarrow\)\(x=\frac{14}{15}\)
Vậy GTNN của F = - 19 đạt được khi x = \(\frac{14}{15}\)