Для какого числа х верно равенство?
а)
$$
\begin{array}{@l|l}
\begin{array}{l}
x + 13 = 7,\\
x = 7 - 13,\\
x = -6;
\end{array}
&
\begin{array}{l}
7 - 13 = -(13 - 7) = -6\\
\end{array}
\end{array}
$$
б) х + 8 = −7;
в) −7 + х = 9;
г) х − (−8) = 13;
д) −15 − х = 7.
Решение:
б) $
\begin{array}{@l|l}
\begin{array}{l}
x + 8 = -7\\
x = -7 - 8\\
x = -15;
\end{array}
&
\begin{array}{l}
-15 + 8 = -(15 - 8) = -7\\
\end{array}
\end{array}
$;
в) $
\begin{array}{@l|l}
\begin{array}{l}
-7 + x = 9\\
x = 9 - (-7)\\
x = 9 + 7\\
x = 16;
\end{array}
&
\begin{array}{l}
-7 + 16 = +(16 - 7) = 9\\
\end{array}
\end{array}
$;
г) $
\begin{array}{@l|l}
\begin{array}{l}
x - (-8) = 13\\
x + 8 = 13\\
x = 13 - 8\\
x = 5;
\end{array}
&
\begin{array}{l}
5 - (-8) = 5 + 8 = 13\\
\end{array}
\end{array}
$;
д) $
\begin{array}{@l|l}
\begin{array}{l}
-15 - x = 7\\
x = -15 - 7\\
x = -(15 + 7)\\
x = -22;
\end{array}
&
\begin{array}{l}
-15 - (-22) = -15 + 22 = +(22 - 15) = 7\\
\end{array}
\end{array}
$.
Ответ:
б) −15;
в) 16;
г) 5;
д) −22.
Пожауйста, оцените решение
