\[\boxed{\mathbf{775}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\]
\[a\] | \[b\] | \[a - b\] | \[b - a\] |
---|---|---|---|
\[20\] | \[7\] | \[20 - 7 = 20 + ( - 7) = 13\] | \[7 - 20 = 7 + ( - 20) = - 13\] |
\[- 15\] | \[8\] | \[- 15 - 8 = - 23\] | \[8 - ( - 15) = 8 + 15 = 23\] |
\[30\] | \[- 9\] | \[30 - ( - 9) = 30 + 9 = 39\] | \[- 9 - 30 = - 39\] |
\[- 10\] | \[- 6\] | \[- 10 - ( - 6) = - 10 + 6 = - 4\] | \[- 6 - ( - 10) = - 6 + 10 = 4\] |
\[2)\ Значения\ выражений\ (a - b)\ и\ \ (b - a)\ являются\ противоположными.\]
\[3)\ x - y = 30\]
\[x - y = - (y - x)\]
\[Значит:\ \ \ \ \ \ y - x = - (x - y) = - 30.\]
\[Ответ:\ - 30.\]