[13^21+13^19]/[13^15.4]
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21.(19-13) - 19(21-13)
= 21.19 - 21.13 - 19.21 + 19.13
= ( 21.19 - 19.21) - 13.( 21 - 19)
= 0 - 13. 2
= - 26
a: \(=2+\dfrac{13}{19}+\dfrac{8}{21}-\dfrac{13}{19}+\dfrac{7}{2}+\dfrac{13}{21}\)
\(=2+\dfrac{7}{2}+1=3+\dfrac{7}{2}=\dfrac{13}{2}\)
b: \(=\dfrac{11}{25}\left(-192-150\right)=\dfrac{11}{25}\cdot\left(-342\right)=-\dfrac{3762}{25}\)
a) \(\frac{58}{19}+\frac{13}{17}+\frac{35}{43}+\frac{119}{19}+\frac{8}{43}\)
\(=\frac{13}{17}+\left(\frac{58}{19}+\frac{119}{19}\right)+\left(\frac{35}{43}+\frac{8}{43}\right)\)
\(=\frac{13}{17}+\frac{204}{19}+1\)
\(=\frac{1808}{133}\)
b) \(\frac{-5}{7}.\frac{2}{11}+\frac{-5}{7}.\frac{9}{11}+\frac{13}{4}\)
\(=\frac{-5}{7}.\left(\frac{2}{11}+\frac{9}{11}\right)+\frac{13}{4}\)
\(=\frac{-5}{7}.1+\frac{13}{4}\)
\(=\frac{71}{28}\)
c) \(\frac{146}{13}-\left(\frac{21}{7}+\frac{68}{13}\right)\)
\(=\left(\frac{164}{13}-\frac{68}{13}\right)+3\)
\(=\frac{135}{13}\)
d) \(\frac{2}{7}.\frac{21}{4}-\frac{2}{7}.\frac{13}{4}\)
\(=\frac{2}{7}.\left(\frac{21}{4}-\frac{13}{4}\right)\)
\(=\frac{2}{7}.\frac{8}{4}\)
\(=\frac{4}{7}\)
P/s: Mk ko chắc nữa!
b: \(=\dfrac{-5}{7}\left(\dfrac{2}{11}+\dfrac{9}{11}\right)+\dfrac{13}{4}=\dfrac{-5}{7}+\dfrac{13}{4}=\dfrac{-20+91}{28}=\dfrac{71}{28}\)
c: \(=\dfrac{146}{13}-3-\dfrac{68}{13}=6-3=3\)
d: \(=\dfrac{2}{7}\left(\dfrac{21}{4}-\dfrac{13}{4}\right)=\dfrac{4}{7}\)
\(\Leftrightarrow\left(\dfrac{1}{11}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{15}+...+\dfrac{1}{19}-\dfrac{1}{21}\right)\cdot462-y=19\)
\(\Leftrightarrow20-y=19\)
hay y=1