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a) \(12+\frac{x}{42}=\frac{5}{6}\)
\(\frac{x}{42}=\frac{5}{6}-12\)
\(\frac{x}{42}=\frac{-67}{6}\)
\(\frac{x}{42}=\frac{-469}{42}\)
\(\Rightarrow x=-469\)
\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\)\(\frac{1}{6.7}\)=\(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)
=\(\frac{1}{1}-\frac{1}{7}=\frac{6}{7}\)
Tính bằng cách thuận tiện:
\(\frac{13}{7}\)+ \(\frac{5}{6}\)+ \(\frac{2}{7}\)+ \(\frac{7}{6}\) \(\frac{1}{2}\) x \(\frac{5}{6}\)+ \(\frac{1}{2}\)x \(\frac{11}{6}\)
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\(a.\frac{3}{7}.\frac{5}{6}+\frac{5}{6}.\frac{4}{7}=\left(\frac{3}{7}+\frac{4}{7}\right).\frac{5}{6}=1.\frac{5}{6}=\frac{5}{6}\)
\(b.\frac{1}{6}:\frac{4}{5}+\frac{1}{8}:\frac{4}{5}=\left(\frac{1}{6}+\frac{1}{8}\right):\frac{4}{5}=\left(\frac{4}{24}+\frac{3}{24}\right):\frac{4}{5}=\frac{7}{24}:\frac{4}{5}=\frac{7.5}{24.4}\)\(=\frac{35}{96}\)
\(c.\frac{1}{6}:\frac{4}{5}-\frac{1}{8}:\frac{4}{5}=\left(\frac{1}{6}-\frac{1}{8}\right):\frac{4}{5}=\left(\frac{4}{24}-\frac{3}{24}\right):\frac{4}{5}\)\(=\frac{1}{24}:\frac{4}{5}=\frac{1.5}{24.4}=\frac{5}{96}\)
a) \(\frac{3}{7}\cdot\frac{5}{6}+\frac{5}{6}\cdot\frac{4}{7}\)
\(=\left(\frac{3}{7}+\frac{4}{7}\right)\cdot\frac{5}{6}\)
\(=1\cdot\frac{5}{6}\)
\(=\frac{5}{6}\)
b) \(\frac{1}{6}:\frac{4}{5}+\frac{1}{8}:\frac{4}{5}\)
\(=\left(\frac{1}{6}+\frac{1}{8}\right):\frac{4}{5}\)
\(=\frac{7}{24}:\frac{4}{5}\)
\(=\frac{35}{96}\)
c) \(\frac{1}{6}:\frac{4}{5}-\frac{1}{8}:\frac{4}{5}\)
\(=\left(\frac{1}{6}-\frac{1}{8}\right):\frac{4}{5}\)
\(=\frac{1}{24}:\frac{4}{5}\)
\(=\frac{5}{96}\)
Để kết quả của phép tính trên là 0 thì :
\(\frac{32}{46}\)X x - \(\frac{16}{23}\)X \(\frac{21}{23}\)= 0
\(\frac{16}{23}\)X x - \(\frac{16}{23}\)X \(\frac{21}{23}\)= 0
\(\frac{16}{23}\)X ( x - \(\frac{21}{23}\)) = 0
x - \(\frac{21}{23}\)= 0 ( chia cả 2 vế cho \(\frac{16}{23}\))
x = 0 + \(\frac{21}{23}\)
x = \(\frac{21}{23}\)
Vậy x = \(\frac{21}{23}\)
rẻ rách quá ko thèm làm vì quá dẽ
(12+X)x6=42x5
(12+X)x6=210
12+X=210:6
12+X=35.
X=35-12=23.
Vậy X=23