Question

19 баллов
-1/20+2/30-3/20+4/30

Answer 1

$- \frac{1}{20} + \frac{2}{30} - \frac{3}{20} + \frac{4}{30} = ( - \frac{1}{20} - \frac{3}{20} ) + ( \frac{2}{30} + \frac{4}{30} ) = - \frac{4}{20} + \frac{6}{30} = - \frac{1}{5} + \frac{1}{5} = 0$

Answer 2

$\displaystyle -\frac{1}{20}+\frac{2}{30}-\frac{3}{20}+\frac{4}{30}=\frac{-1-3}{20}+\frac{2+4}{30}=\frac{-4}{20}+\frac{6}{30}=-\frac{1}{5}+\frac{1}{5}=0$