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a)=\(\frac{7}{30}\)-\(\frac{17}{12}\)=\(\frac{-71}{60}\) b) = \(\frac{29}{20}\)+\(\frac{-31}{30}\)+\(\frac{-2}{3}=\frac{-1}{4}\)
a)\(\frac{2}{3}+\frac{3}{4}+\frac{5}{6}\)
\(=\frac{8+9+10}{12}\)
\(=\frac{27}{12}=\frac{9}{4}\)
b)\(\frac{15}{8}-\frac{7}{12}+\frac{5}{6}\)
\(=\frac{45-14+20}{24}\)
\(=\frac{51}{24}=\frac{17}{8}\)
2)
a)\(\frac{2}{5}+\frac{7}{13}+\frac{3}{5}+\frac{1}{7}\)
\(=\frac{2}{5}+\frac{3}{5}+\frac{7}{13}+\frac{1}{7}\)
\(=1+\frac{7}{13}+\frac{1}{7}\)
\(=\frac{20}{13}+\frac{1}{7}\)
\(=\frac{153}{91}\)
Tí tớ trả lời tiếp
\(6\frac{5}{12}:2\frac{3}{4}+11\frac{1}{4}.\left(\frac{1}{3}-\frac{1}{5}\right)\)
\(=\frac{77}{12}:\frac{11}{4}+\frac{45}{4}.\left(\frac{5}{15}-\frac{3}{15}\right)\)
\(=\frac{77}{12}.\frac{4}{11}+\frac{45}{4}.\frac{2}{15}\)
\(=\frac{7}{3}+\frac{3}{2}\)
\(=\frac{14}{6}+\frac{9}{6}\)
\(=\frac{23}{6}=3\frac{5}{6}\)
\(\left(\frac{3}{8}+-\frac{3}{4}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)
\(=\left(\frac{9}{24}+-\frac{18}{24}+\frac{14}{24}\right):\frac{5}{6}+\frac{1}{2}\)
\(=\frac{5}{24}:\frac{5}{6}+\frac{1}{2}\)
\(=\frac{5}{24}.\frac{6}{5}+\frac{1}{2}\)
\(=\frac{1}{4}+\frac{1}{2}\)
\(=\frac{1}{4}+\frac{2}{4}\)
\(=\frac{3}{4}\)
\(\frac{1}{2}+\frac{3}{4}-\left(\frac{3}{4}-\frac{4}{5}\right)\)
\(=\frac{1}{2}+\frac{3}{4}-\left(\frac{15}{20}-\frac{16}{20}\right)\)
\(=\frac{1}{2}+\frac{3}{4}-\frac{-1}{20}\)
\(=\frac{10}{20}+\frac{15}{20}-\frac{-1}{20}\)
\(=\frac{25}{20}-\frac{-1}{20}\)
\(=\frac{26}{20}\)
\(=\frac{13}{10}\)
1-2+3-4+5-6+...+2011-2012
=2012-2011+...+6-5+4-3+2-1
=(2012-2001)+...+(6-5)+(4-3)+(2-1)
=1+1+1+...+1+1(có 1006 số 1)
=1x60
=60
\(\frac{3}{4}+\frac{5}{6}-\left(\frac{3}{4}+\frac{1}{2}\right)=\frac{3}{4}+\frac{5}{6}-\frac{3}{4}-\frac{1}{2}\)
\(=\frac{5}{6}-\frac{3}{6}\)
=\(\frac{2}{6}\)
=\(\frac{1}{3}\)
Chúc bạn học tốt+-*/
\(\frac{3}{4}+\frac{5}{6}-\frac{3}{4}-\frac{1}{2}=\left(\frac{3}{4}-\frac{3}{4}\right)-\left(\frac{5}{6}+\frac{1}{2}\right)=0-\frac{4}{3}=-\frac{4}{3}\)