Question

ДАЮ 35 БАЛЛОВ!!!! С РЕШЕНИЕМ!!!

Answer 1

$\frac{1}{25} {c}^{2} - \frac{9}{169} {d}^{2} = ( \frac{1}{5} c) ^{2} - {( \frac{3}{13}d) }^{2} = \\ = ( \frac{1}{5} c - \frac{3}{13} d)( \frac{1}{5} c + \frac{3}{13} d)$