Question

помогите пж пж. даю 50 балов​

Answer 1

$\frac{7}{m + n} = \frac{7 \times (m - n)}{(m - n)( m+ n)} = \frac{7m - 7n}{ {m}^{2} - {n}^{2} } \\ \frac{7}{m + n} = \frac{7 \times (m + n)}{(m + n)( m+ n)} = \frac{7m + 7n}{ {m}^{2} + 2mn + {n}^{2} } \\ \frac{7}{m + n} = \frac{7 \times m}{m( m+ n)} = \frac{7m}{ {m}^{2} - mn}$