Đáp án:
Giải thích các bước giải:
1
$\frac{1}{6}+\frac{2}{5}=\frac{17}{30}\\\frac{3}{5}+(-\frac{7}{4})=-\frac{23}{20}\\\frac{4}{13}+(-\frac{2}{39})=\frac{10}{39}\\-\frac{8}{18}+(-\frac{15}{27})=-1$
2)
a) $-\frac{2}{5}+\frac{3}{-4}+\frac{6}{7}+\frac{3}{4}+\frac{2}{5}\\=(\frac{2}{5}-\frac{2}{5})+(\frac{3}{4}-\frac{3}{4})+\frac{6}{7}\\=\frac{6}{7}$
b) $-\frac{1}{8}+\frac{7}{9}+(-\frac{7}{8})+\frac{6}{7}+\frac{2}{14}\\=-1+\frac{1}{7}+\frac{6}{7}+\frac{7}{9}\\=-1+1+\frac{7}{9}\\=\frac{7}{9}$
c) $\frac{5}{11}+\frac{16}{22}+(-\frac{12}{4})+(-\frac{2}{11})\\=\frac{5}{11}+\frac{8}{11}-\frac{12}{4}-\frac{2}{11}\\=(\frac{5}{11}+\frac{8}{11}-\frac{2}{11})-\frac{12}{4}\\=1-3\\=-2$
d) $\frac{7}{23}+(-\frac{10}{18})+(-\frac{4}{9})+\frac{16}{23}\\=(\frac{7}{23}+\frac{16}{23})-(\frac{5}{9}+\frac{4}{9})\\=1-1\\=0$
