21011中２・式の計算・計算問題・同類項をまとめる1

$\begin{eqnarray}(1)\;\;3x+2+6x-5&=&3x+6x+2-5\\[5pt]&=&(\,3+6\,)x-3\\[5pt]&=&9x-3\end{eqnarray}\;\;$

答$9x-3$

$\begin{eqnarray}(2)\;\;x-5y+3x-2y&=&x+3x-5y-2y\\[5pt]&=&(\,1+3\,)x+(\,-5-2\,)y\\[5pt]&=&4x-7y\end{eqnarray}\;\;$

答$4x-7y$

$\begin{eqnarray}(3)\quad\;\;6a-4b-5+5a-7b-1\end{eqnarray}\;\;$

$\quad\;\;\begin{eqnarray}&=&6a+5a-4b-7b-5-1\\[6pt]&=&11a-11b-6\end{eqnarray}\;\;$

答$11a-11b-6$

$\begin{eqnarray}(4)\quad\;\;-x^{2}-4x+3+5x-2+6x^{2}\end{eqnarray}\;\;$

$\quad\;\;\begin{eqnarray}&=&-x^{2}+6x^{2}-4x+5x+3-2\\[6pt]&=&5x^{2}+x+1\end{eqnarray}\;\;$

答$5x^{2}+x+1$

$\begin{eqnarray}(5)\quad\;\;-6ab+4a^{2}+3b^{2}+7ab-5a^{2}+2b^{2}\end{eqnarray}\;\;$

$\quad\;\;\begin{eqnarray}&=&4a^{2}-5a^{2}-6ab+7ab+3b^{2}+2b^{2}\\[6pt]&=&-a^{2}+ab+5b^{2}\end{eqnarray}\;\;$

答$-a^{2}+ab+5b^{2}$