номер 78 гдз 8 класс алгебра Муравин Муравина

1)\begin{equation}\frac{10-x}{x-7}+\frac{2x-11}{7-x} \end{equation} \begin{equation}\frac{10-x}{x-7}-\frac{2x-11}{x-7}=\frac{10-x-2x+11}{x-7}= \end{equation} \begin{equation}=\frac{21-3x}{x-7}=\frac{3\left ( 7-x \right )}{x-7}=-3 \end{equation} 2)\begin{equation}\frac{11y-8}{y^{2}-25}+\frac{12+7y}{25-y^{2}} \end{equation} \begin{equation}\frac{11y-8}{y^{2}-25}-\frac{12+7y}{y^{2}-25}= \end{equation} \begin{equation}=\frac{11y-8-12-7y}{y^{2}-25}=\frac{4y-20}{y^{2}-25}= \end{equation} \begin{equation}=\frac{4\left ( y-5 \right )}{\left ( y-5 \right )\left ( y+5 \right )}=\frac{4}{y+5} \end{equation} 3)\begin{equation}\frac{a^{2}-13a}{a^{2}-36}-\frac{36+a}{36-a^{2}} \end{equation} \begin{equation}-\frac{a^{2}-13a}{36-a^{2}}-\frac{36+a}{36-a^{2}}= \end{equation} \begin{equation}=\frac{-a^{2}+13a-36-a}{36-a^{2}}=\frac{12a-36-a^{2}}{36-a^{2}}= \end{equation} \begin{equation}=\frac{-\left ( a^{2}-12a+36 \right )}{-\left ( a^{2}-36 \right )}= \end{equation} \begin{equation}=\frac{\left ( a-6 \right )^{2}}{\left ( a-6 \right )\left ( a+6 \right )}=\frac{a-6}{a+6} \end{equation} 4)\begin{equation}\frac{b^{2}+8b}{49-b^{2}}-\frac{6b+49}{b^{2}-49} \end{equation} \begin{equation}-\frac{b^{2}+8b}{b^{2}-49}-\frac{6b+49}{b^{2}-49}= \end{equation} \begin{equation} =\frac{-b^{2}-8b-6b-49}{b^{2}-49}= \end{equation} \begin{equation}=\frac{-b^{2}-14b-49}{b^{2}-49}=\frac{-\left ( b^{2}+14b+49 \right )}{b^{2}-49}= \end{equation} \begin{equation}=-\frac{\left ( b+7 \right )^{2}}{\left ( b-7 \right )\left ( b+7 \right )}=-\frac{b+7}{b-7} \end{equation}
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