Question

((m + 7)/m - (n + 7)/n) * (mn)/(m ^ 2 - n ^ 2) пожалуйста фото дам 40 б​

Answer 1

$\displaystyle\bf\\\Bigg(\frac{m+7}{m} -\frac{n+7}{n} \Bigg)\cdot\frac{mn}{m^{2} - n^{2} } =\\\\\\=\frac{(m+7)\cdot n-(n+7)\cdot m}{mn} \cdot\frac{mn}{m^{2} - n^{2} } =\\\\\\=\frac{mn+7n-mn-7m}{(m-n)\cdot(m+n)} =\frac{7n-7m}{(m-n)\cdot(m+n)} =\\\\\\=\frac{7\cdot(n-m)}{(m-n)\cdot(m+n)} =-\frac{7}{m+n}$