quy đồng mẫu số các phân số sau :
a) 8 / 15 ; -7 / 18 ; 13 / 90
b) 5 / 12 ; -11 / 15 ; 49 / -60
c) 7 / 30 ; 13 / 60 ; -9 / -40
d) 17 / 60 ; -5 / 18 ; -64 / 90
quy đồng mẫu số các phân số sau : a) 8 / 15 ; -7 / 18 ; 13 / 90 b) 5 / 12 ; -11 / 15 ; 49 / -60 c) 7 / 30 ; 13 / 60 ; -9 / -40 d) 17 / 60 ; -5 / 18 ;
By Remi
a) $\frac{8}{15}$ ; $\frac{-7}{18}$ ; $\frac{13}{90}$
MC=90
$\frac{8}{15}$=$\frac{8.6}{15.6}$=$\frac{48}{90}$
$\frac{-7}{18}$=$\frac{-7.5}{18.5}$=$\frac{-35}{90}$
b) $\frac{5}{12}$;$\frac{-11}{15}$;$\frac{49}{-60}$
$\frac{49}{-60}$=$\frac{-49}{60}$
MC=60
$\frac{5}{12}$=$\frac{5.5}{12.5}$=$\frac{25}{60}$
$\frac{-11}{15}$=$\frac{-11.4}{15.4}$=$\frac{-44}{60}$
c) $\frac{7}{30}$;$\frac{13}{60}$;$\frac{-9}{-40}$
$\frac{-9}{-40}$=$\frac{9}{40}$
MC=120
$\frac{7}{30}$=$\frac{7.4}{30.4}$=$\frac{28}{120}$
$\frac{13}{60}$=$\frac{13.2}{60.2}$=$\frac{26}{120}$
$\frac{9}{40}$=$\frac{9.3}{40.3}$= $\frac{27}{120}$
d) $\frac{17}{60}$;$\frac{-5}{18}$;$\frac{-64}{90}$
$\frac{-64}{90}$=$\frac{-32}{45}$
MC=180
$\frac{17}{60}$=$\frac{17.3}{60.3}$=$\frac{51}{180}$
$\frac{-5}{18}$=$\frac{-5.10}{18.10}$=$\frac{-50}{180}$
$\frac{-32}{45}$=$\frac{-32.4}{45.4}$= $\frac{-128}{180}$
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