a: \(\frac{5}{12}=\frac{5\times21}{12\times21}=\frac{105}{252}\)
\(\frac{7}{18}=\frac{7\times14}{18\times14}=\frac{98}{252}\)
\(\frac{-8}{21}=\frac{-8\times12}{21\times12}=\frac{-96}{252}\)
\(\frac{-5}{14}=\frac{-5\times18}{14\times18}=\frac{-90}{252}\)
mà -96<-90<98<105
nên \(-\frac{8}{21}<-\frac{5}{14}<\frac{7}{18}<\frac{5}{12}\)
b: \(\frac{7}{41}=\frac{7\times42}{41\times42}=\frac{294}{1722}\)
\(\frac{14}{105}=\frac{14\times21}{105\times21}=\frac{294}{2205}\)
\(\frac{49}{280}=\frac{49\times6}{280\times6}=\frac{294}{1680}\)
\(\frac{21}{126}=\frac{21\times14}{126\times14}=\frac{294}{1764}\)
mà 1680<1722<1764<2205
nên \(\frac{294}{1680}>\frac{294}{1722}>\frac{294}{1764}>\frac{294}{2205}\)
=>\(\frac{49}{280}>\frac{7}{41}>\frac{21}{126}>\frac{14}{105}\)
