Đáp án:

$\displaystyle \begin{array}{{>{\displaystyle}l}} Bài\ 1:\\ a.\ -2;\ b.\ \frac{5}{4} ;\ c.\ \frac{1}{63} ;\ d.\ \frac{13}{30} ;\ e.\ \frac{-1}{12}\\ f.\ \frac{1}{12} ;\ g.\ \frac{-23}{4} ;\ h.\ \frac{-1}{4} ;\ i.\ \frac{-1}{5} ;\ j.\ \frac{1}{63}\\ Bài\ 2:\\ a.\ \frac{4}{11} ;\ b.\ \frac{56}{15} ;\ c.\ \frac{2}{15} ;\ d.\ \frac{-1}{2} ;\ e.\ \frac{-1}{5}\\ f.\ \frac{10}{3} ;\ g.\ \frac{-13}{6} ;\ h.\ \frac{-2}{3} ;\ i.\ \frac{-5}{14} ;\ j.\ \frac{-3}{2} \end{array}$

Giải thích các bước giải:

$\displaystyle \begin{array}{{>{\displaystyle}l}} Câu\ 1:\\ a.\ \frac{1}{2} -\frac{5}{2} =\frac{1-5}{2} =\frac{-4}{2} =-2\\ b.\ \frac{1}{2} +\frac{3}{4} =\frac{2}{4} +\frac{3}{4} =\frac{2+3}{4} =\frac{5}{4}\\ c.\ -\frac{5}{9} +\frac{4}{7} =\frac{-5.7+4.9}{63} =\frac{1}{63}\\ d.\ \frac{1}{3} +\frac{1}{10} =\frac{10}{30} +\frac{3}{30} =\frac{13}{30}\\ e.\ \frac{1}{6} -\frac{1}{4} =\frac{4}{24} -\frac{6}{24} =\frac{-2}{24} =\frac{-1}{12}\\ f.\ \frac{1}{21} -\frac{-1}{28} =\frac{4}{84} +\frac{3}{84} =\frac{7}{84} =\frac{1}{12}\\ g.\ -2\frac{1}{2} -3\frac{1}{4} =\frac{-5}{2} -\frac{13}{4} =\frac{-10}{4} -\frac{13}{4} =\frac{-23}{4}\\ h.\ 0,5-\frac{3}{4} =\frac{1}{2} -\frac{3}{4} =\frac{2}{4} -\frac{3}{4} =\frac{-1}{4}\\ i.\ \frac{1}{5} -0,4=\frac{1}{5} -\frac{2}{5} =\frac{-1}{5}\\ j.\ \frac{-5}{9} +\frac{4}{7} =\frac{-35}{63} +\frac{36}{63} =\frac{1}{63}\\ Bài\ 2:\\ a.\ \frac{8}{10} .\frac{5}{11} =\frac{2.4.5}{5.2.11} =\frac{4}{11}\\ b.\ \frac{7}{5} .\frac{8}{3} =\frac{7.8}{5.3} =\frac{56}{15}\\ c.\ \frac{36}{35} .\frac{7}{54} =\frac{2^{2} .3^{2} .7}{5.7.3^{3} .2} =\frac{2}{5.3} =\frac{2}{15}\\ d.\ \frac{5}{3} .\frac{-3}{10} =\frac{5.( -3)}{3.5.2} =\frac{-1}{2}\\ e.\ -\frac{3}{20} :\frac{3}{4} =-\frac{3}{4.5} .\frac{4}{3} =-\frac{1}{5}\\ f.\ \frac{-5}{2} :\frac{3}{-4} =\frac{-5}{2} .\frac{-2.2}{3} =\frac{10}{3}\\ g.\ -\frac{13}{10} :\frac{3}{5} =-\frac{13}{5.2} .\frac{5}{3} =\frac{-13}{6}\\ h.\ \frac{-8}{15} .1\frac{1}{4} =\frac{-8}{15} .\frac{5}{4} =\frac{-2^{3} .5}{5.3.2^{2}} =\frac{-2}{3}\\ i.\ 1,25:( -3,5) =\frac{5}{4} :\frac{-7}{2} =\frac{5}{2^{2}} .\frac{2}{-7} =\frac{-5}{14}\\ j.\ 4\frac{1}{5} :\left( -2\frac{4}{5}\right) =\frac{21}{5} :\frac{-14}{5} =\frac{3.7}{5} .\frac{5}{-2.7} =\frac{-3}{2} \end{array}$