\[\boxed{\mathbf{756\ (756)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\]
\[a\] | \[b\] | \[- (a + b)\] | \[( - a) + ( - b)\] |
---|---|---|---|
\[20\] | \[15\] | \[- (20 + 15) = - 35\] | \[( - 20) + ( - 15) = - 35\] |
\[- 20\] | \[- 15\] | \[- \left( ( - 20) + ( - 15) \right) = 35\] | \[- ( - 20) + \left( - ( - 15) \right) = 35\] |
\[- 20\] | \[15\] | \[- \left( ( - 20) + 15 \right) = - ( - 5) = 5\] | \[- ( - 20) + ( - 15) = 5\] |
\[20\] | \[- 15\] | \[- \left( 20 + ( - 15) \right) = - 5\] | \[( - 20) + \left( - ( - 15) \right) = - 5\] |
\[2) - (a + b) \Longrightarrow число,\ противоположное\ сумме\ a\ и\ b.\]
\[( - a) + ( - b) \Longrightarrow сумма\ чисел,\ противоположных\ числам\ a\ и\ b.\]
\[Вывод\ по\ результатам\ вычислений:\ - (a + b) = ( - a) + ( - b).\]
\[3)\ x + y = 50\]
\[Значит:\ \ \ \ \ - (x + y) = - 50.\]
\[- (x + y) = ( - x) + ( - y) = - 50.\]
\[Ответ:\ - 50.\]