Question

Tính một cách hợp lí:

a)\(\dfrac{-5}{12}+\left(-37\right)-\dfrac{7}{12}-6,3\)               b)\(2,8.\left(\dfrac{-6}{13}\right)-7,2-2,8.\dfrac{7}{13}\)

 

 

Answer 1

a)

\(\begin{array}{l}\frac{{ - 5}}{{12}} + \left( { - 3,7} \right) - \frac{7}{{12}} - 6,3\\ = \left( {\frac{{ - 5}}{{12}} - \frac{7}{{12}}} \right) - \left( {3,7 + 6,3} \right)\\ =\frac{-12}{12}-10\\=  - 1 - 10 \\=  - 11\end{array}\)      

b)

\(\begin{array}{l}2,8.\frac{{ - 6}}{{13}} - 7,2 - 2,8.\frac{7}{{13}}\\ = 2,8.\left( {\frac{{ - 6}}{{13}} - \frac{7}{{13}}} \right) - 7,2\\= 2,8.\frac{-13}{13}- 7,2\\ = 2,8.\left( { - 1} \right) - 7,2\\ =  - 2,8 - 7,2\\ =  - 10\end{array}\)