Ta có : \(8=2^3;27=3^3\)
\(\Rightarrow BCNN\left(8,27\right)=2^3.3^3=216\)
\(\frac{3}{8}=\frac{3.27}{8.27}=\frac{81}{216}\)
\(\frac{5}{27}=\frac{5.8}{27.8}=\frac{40}{216}\)
b, Ta có : \(9=3^2;25=5^2\)
\(\Rightarrow BCNN\left(9,25\right)=3^2.5^2=225\)
\(\frac{-2}{9}=\frac{-2.25}{9.25}=\frac{-50}{225}\)
\(\frac{4}{25}=\frac{4.9}{25.9}=\frac{36}{225}\)
1 ) a ) \(\frac{3}{8}\) và \(\frac{5}{27}\)
BCNN( 8 ; 7 ) = \(8=2^3;27=3^3\)=\(2^3.3^3=8.27=216\)
Thừa số phụ tương ứng : 27 ; 8 .
nên \(\frac{3}{8}=\frac{3.27}{8.27}=\frac{81}{216}\)
\(\frac{5}{27}=\frac{5.8}{27.8}=\frac{40}{216}\)
b) \(\frac{-2}{9}\) và \(\frac{4}{25}\)
BCNN ( 9 ; 25 ) = \(9=3^2;25=5^2=3^2.5^2=225\)
Thừa số phụ tương ứng : 25 ; 9 .
nên : \(\frac{-2}{9}=\frac{\left(-2\right).25}{9.25}=\frac{-50}{225}\)
\(\frac{4}{25}=\frac{4.9}{25.9}=\frac{36}{225}\)