Question

1a) \(\dfrac{-2}{9}\)+\(\dfrac{7}{-9}\)
b)  \(\dfrac{1}{-6}\)+\(\dfrac{13}{-15}\)
c)  \(\dfrac{5}{-6}\)+\(\dfrac{5}{-6}\)+\(\dfrac{7}{18}\)

2a) \(\dfrac{2}{9}\)+\(\dfrac{-3}{10}\)+\(\dfrac{-7}{10}\)
 b) \(\dfrac{-11}{6}\)+\(\dfrac{2}{5}\)+\(\dfrac{-1}{6}\)
 c) \(\dfrac{-5}{8}\)+\(\dfrac{12}{7}\)+\(\dfrac{13}{8}\)+\(\dfrac{2}{7}\)
giúp mình với!!!!!!

Answer 1

1.
a)\(-\dfrac{2}{9}+\dfrac{7}{-9}=-1\)
b)\(\dfrac{1}{-6}+\dfrac{13}{-15}=-\dfrac{5}{30}+-\dfrac{26}{30}=-\dfrac{31}{30}\)
c)\(\dfrac{5}{-6}+\dfrac{5}{-6}+\dfrac{7}{18}=-\dfrac{5}{3}+\dfrac{7}{18}=\dfrac{7}{18}-\dfrac{30}{18}=-\dfrac{23}{18}\)
2.
a)\(\dfrac{2}{9}+-\dfrac{3}{10}+-\dfrac{7}{10}\)
\(=\dfrac{2}{9}+\left(-\dfrac{3}{10}+-\dfrac{7}{10}\right)\)
\(=\dfrac{2}{9}+-1\)
\(=\dfrac{2}{9}-1=\dfrac{2}{9}-\dfrac{9}{9}=-\dfrac{7}{9}\)
b)\(-\dfrac{11}{6}+\dfrac{2}{5}+-\dfrac{1}{6}\)
\(=\left(-\dfrac{11}{6}+-\dfrac{1}{6}\right)+\dfrac{2}{5}\)
\(=-2+\dfrac{2}{5}\)
\(=\dfrac{2}{5}-2=\dfrac{2}{5}-\dfrac{10}{5}=-\dfrac{8}{5}\)
c)\(-\dfrac{5}{8}+\dfrac{12}{7}+\dfrac{13}{8}+\dfrac{2}{7}\)
\(=\left(-\dfrac{5}{8}+\dfrac{13}{8}\right)+\left(\dfrac{12}{7}+\dfrac{2}{7}\right)\)
\(=1+2=3\)

Answer 2

1. 

\(a,\dfrac{-2}{9}+\dfrac{7}{-9}=\dfrac{-2}{9}+\dfrac{-7}{9}=\dfrac{-9}{9}=-1\)

\(b,\dfrac{1}{-6}+\dfrac{13}{-15}=\dfrac{-5}{30}+\dfrac{-26}{30}=\dfrac{-31}{30}\)

\(c,\dfrac{5}{-6}+\dfrac{5}{-6}+\dfrac{7}{18}=\dfrac{-10}{6}+\dfrac{7}{18}=\dfrac{-30}{18}+\dfrac{7}{18}=\dfrac{-23}{18}\)

2. 

\(a,\dfrac{2}{9}+\dfrac{-3}{10}+\dfrac{-7}{10}=\dfrac{2}{9}+\left(-1\right)=\dfrac{2}{9}+\dfrac{-9}{9}=\dfrac{-7}{9}\)

\(b,\dfrac{-11}{6}+\dfrac{2}{5}+\dfrac{-1}{6}=\dfrac{2}{5}+\left(-2\right)=\dfrac{2}{5}+\dfrac{-10}{5}=\dfrac{-8}{5}\)

\(c,\dfrac{-5}{8}+\dfrac{12}{7}+\dfrac{13}{8}+\dfrac{2}{7}=\left(\dfrac{-5}{8}+\dfrac{13}{8}\right)+\left(\dfrac{12}{7}+\dfrac{2}{7}\right)=1+2=3\)