21051中２・式の計算・計算問題・単項式の除法1

$\begin{eqnarray}(1)\quad\;\;xy \div y\end{eqnarray}\;\;$

$\begin{eqnarray}\quad\;\;&=&\dfrac{\,x \times \color{red}\cancelto{1}{\color{black}y}\,}{\,\color{red}\cancelto{1}{\color{black}y}\,}\\[6pt]&=&x\end{eqnarray}\;\;$

答$x$

$\begin{eqnarray}(2)\quad\;\;2ab \div (\,-ab\,)\end{eqnarray}\;\;$

$\begin{eqnarray}\quad\;\;&=&-\dfrac{\,2 \times \color{red}\cancelto{1}{\color{black}a} \color{black}\times \color{aqua}\cancelto{1}{\color{black}b}\,}{\,\color{red}\cancelto{1}{\color{black}a} \color{black}\times \color{aqua}\cancelto{1}{\color{black}b}\,}\\[6pt]&=&-2\end{eqnarray}\;\;$

答$-\,2$

$\begin{eqnarray}(3)\quad\;\;(\,-4xy\,) \div 2x\end{eqnarray}\;\;$

$\begin{eqnarray}\quad\;\;&=&-\dfrac{\,\color{silver}\cancelto{2}{\color{black}4} \color{black}\times \color{red}\cancelto{1}{\color{black}x} \color{black}\times y\,}{\,\color{silver}\cancelto{1}{\color{black}2} \color{black}\times \color{red}\cancelto{1}{\color{black}x}\,}\\[6pt]&=&-2y\end{eqnarray}\;\;$

答$-\,2y$

$\begin{eqnarray}(4)\quad\;\;6ab \div (\,-8ab\,)\end{eqnarray}\;\;$

$\begin{eqnarray}\quad\;\;&=&-\dfrac{\,\color{silver}\cancelto{3}{\color{black}6} \color{black}\times \color{red}\cancelto{1}{\color{black}a} \color{black}\times \color{aqua}\cancelto{1}{\color{black}b}\,}{\,\color{silver}\cancelto{4}{\color{black}8} \color{black}\times \color{red}\cancelto{1}{\color{black}a} \color{black}\times \color{aqua}\cancelto{1}{\color{black}b}\,}\\[6pt]&=&-\dfrac{3}{\;4\;}\end{eqnarray}\;\;$

答$-\,\dfrac{3}{\;4\;}$

$\begin{eqnarray}(5)\quad\;\;(\,-6xyz\,) \div (\,-2xz\,)\end{eqnarray}\;\;$

$\begin{eqnarray}\quad\;\;&=&+\dfrac{\,\color{silver}\cancelto{3}{\color{black}6} \color{black}\times \color{red}\cancelto{1}{\color{black}x} \color{black}\times y \times \color{aqua}\cancelto{1}{\color{black}z}\,}{\,\color{silver}\cancelto{1}{\color{black}2} \color{black}\times \color{red}\cancelto{1}{\color{black}x} \color{black}\times \color{aqua}\cancelto{1}{\color{black}z}\,}\\[6pt]&=&3y\end{eqnarray}\;\;$

答$3y$