2/3 + 7/5 - 3/5 = .........
13/6 + 5/3 - 2 = .........
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`@` `\text {Ans}`
`\downarrow`
\(\left(x-\dfrac{1}{5}\right)^2+1=3,5\div7\%\)
`=> (x-1/5)^2 + 1 = 3,5 \div 0,07`
`=> (x-1/5)^2 +1=50`
`=> (x-1/5)^2 = 49`
`=> (x-1/5)^2 = (+-7)^2`
`=>`\(\left[{}\begin{matrix}x-\dfrac{1}{5}=7\\x-\dfrac{1}{5}=-7\end{matrix}\right.\)
`=>`\(\left[{}\begin{matrix}x=7+\dfrac{1}{5}\\x=-7+\dfrac{1}{5}\end{matrix}\right.\)
`=>`\(\left[{}\begin{matrix}x=\dfrac{36}{5}\\x=-\dfrac{34}{5}\end{matrix}\right.\)
Vậy, `x={36/5; -34/5}.`
\(\frac{3}{5}-\frac{-7}{10}-\frac{13}{-20}=\frac{3}{5}+\frac{7}{10}+\frac{13}{20}=\frac{12}{20}+\frac{14}{20}+\frac{13}{20}=\frac{39}{20}\)
\(\frac{1}{2}+\frac{-1}{3}+\frac{1}{4}-\frac{-1}{6}=\frac{1}{2}+\frac{-1}{3}+\frac{1}{4}+\frac{1}{6}=\frac{6+(-4)+3+2}{12}=\frac{7}{12}\)
\(\frac{9}{4}.\frac{8}{27}.\frac{5}{7}=\frac{9.8.5}{4.27.7}=\frac{1.2.5}{1.3.7}=\frac{10}{21}\)
\(\frac{2}{5}.(\frac{2}{3}-\frac{1}{4})+\frac{1}{2}=\frac{2}{5}.(\frac{8}{12}-\frac{3}{12})+\frac{1}{2}=\frac{2}{5}.\frac{5}{12}+\frac{1}{2}=\frac{1}{6}+\frac{1}{2}=\frac{1}{6}+\frac{3}{6}=\frac{4}{6}=\frac{2}{3}\)
\((\frac{1}{3}-\frac{1}{6}):(\frac{1}{3}+\frac{1}{6})=(\frac{2}{6}-\frac{1}{6}):(\frac{2}{6}+\frac{1}{6})=\frac{1}{6}:\frac{3}{6}=\frac{1}{6}.\frac{6}{3}=\frac{1.6}{6.3}=\frac{1.1}{1.3}=\frac{1}{3}\)
Hok tốt
\(-\dfrac{5}{7}\times\dfrac{2}{13}+\dfrac{-5}{7}\times\dfrac{3}{13}-\dfrac{5}{7}\times\dfrac{8}{13}\)
\(=-\dfrac{5}{7}\left(\dfrac{2}{13}+\dfrac{3}{13}+\dfrac{8}{13}\right)\)
\(=-\dfrac{5}{7}\times\dfrac{13}{13}\)
\(=-\dfrac{5}{7}\times1=-\dfrac{5}{7}\)
\(\dfrac{-1}{9}.\dfrac{-3}{5}+\dfrac{5}{-6}.\dfrac{-3}{5}-\dfrac{7}{2}.\dfrac{3}{5}\)
\(=\dfrac{3}{5}.\left(\dfrac{1}{9}+\dfrac{5}{6}-\dfrac{7}{2}\right)\)
\(=\dfrac{3}{5}.\left(\dfrac{2}{18}+\dfrac{15}{18}-\dfrac{63}{18}\right)\)
\(=\dfrac{3}{5}.\left(-\dfrac{23}{9}\right)\)
\(=-\dfrac{69}{45}\)
\(C=\dfrac{-5}{7}+\dfrac{-2}{7}+\dfrac{3}{4}+\dfrac{1}{4}+\dfrac{-1}{5}=-1+1-\dfrac{1}{5}=\dfrac{-1}{5}\)
= 10/15+21/15- 9/15
= 31/15 - 9/15
=22/15
\(\dfrac{2}{3}+\dfrac{7}{5}-\dfrac{3}{5}=\dfrac{2}{3}+\dfrac{7-3}{5}=\dfrac{2}{3}+\dfrac{4}{5}=\dfrac{10+12}{15}=\dfrac{22}{15}\)
\(\dfrac{13}{6}+\dfrac{5}{3}-2=\dfrac{13+10}{6}-2=\dfrac{23}{6}-2=\dfrac{23-12}{6}=\dfrac{11}{6}\)