Ta có:

\(\frac{2}{-7}=\frac{-2}{7}=\frac{-22}{77}\)

\(\frac{-3}{11}=\frac{-21}{77}\)

Vì -22 < -21 nên \(\frac{-22}{77}< \frac{-21}{71}\) hay x < y

\(\frac{a}{b}=\frac{ab+a}{b^2+b};\frac{a+1}{b+1}=\frac{ab+b}{b^2+b}\)

\(+,a>b\Rightarrow ab+a>ab+b\Rightarrow\frac{a}{b}>\frac{a+1}{b+1}\left(vì:b>0\right)\)

\(+,a=b\Rightarrow\frac{a}{b}=\frac{a+1}{b+1}=1\)

\(+,a< b\Rightarrow ab+a< ab+b\Rightarrow\frac{a}{b}< \frac{a+1}{b+1}\left(vì:b>0\right)\)

\(Vậy:voi:a>b\text{ thì }\frac{a}{b}>\frac{a+1}{b+1};voi:a=b\text{ thì: }\frac{a}{b}=\frac{a+1}{b+1}=1;voi:a< b\text{ thì:}\frac{a}{b}< \frac{a+1}{b+1}\)

\(\frac{278}{37}=7\frac{19}{37}\); \(\frac{287}{46}=6\frac{11}{46}\).Vì 7 > 6 nên \(7\frac{19}{37}>6\frac{11}{46}\)hay \(\frac{278}{37}>\frac{287}{46}\)

Số hữu tỉ là con cặc mày