Question

tính:

a/ \(\frac{15}{35}\) +   \(\frac{-49}{14}\)+ \(\frac{12}{28}\)

b/ \(\frac{2}{5}\)+\(\frac{7}{10}\) -\(\frac{10}{15}\)

Answer 1

\(a,=\frac{3}{7}+\frac{-7}{2}+\frac{3}{7}\)

\(=\frac{6}{14}+\frac{-49}{14}+\frac{6}{14}\)

\(=\frac{-37}{14}\)

\(b,=\frac{2}{5}+\frac{7}{10}-\frac{2}{3}\)

\(=\frac{12}{30}+\frac{21}{30}-\frac{20}{30}\)

\(=\frac{13}{30}\)

Answer 2

a/ mẫu số chung là 140

=>\(\frac{60}{140}+\frac{-490}{140}+\frac{60}{140}=\frac{60+\left(-490\right)+60}{140}=\frac{-370}{140}\)

b/mẫu số chung là30

=>\(\frac{12}{30}+\frac{21}{30}-\frac{20}{30}=\frac{12+21-20}{30}=\frac{13}{30}\)