Question

Приведите дроби к общему знаменатилю​

Answer 1

1.

$\frac{7a}{b - 13} \\ \frac{b}{169 - b {}^{2} } = - \frac{b}{b {}^{2} - 169 } = - \frac{b}{(b - 13)(b + 13)} \\ \\ \\ \frac{7a}{b - 13} \times ( - \frac{b + 13}{b + 13} ) = - \frac{7ab + 91a}{ {b}^{2} - 169} \\ - \frac{b}{b {}^{2} - 169 }$

2.

$\frac{1}{ {x}^{2} - 2x + 1 } = \frac{1}{( x- 1) {}^{2} } \\ \frac{y}{ {x}^{2} - 1} = \frac{y}{(x - 1)(x + 1)} \\ \\ \frac{1}{ {(x - 1)}^{2} } \times \frac{x + 1}{x + 1} = \frac{x + 1}{(x - 1) { }^{2}(x + 1) } \\ \frac{y}{(x - 1)(x + 1)} \times \frac{ x- 1}{x - 1} = \frac{yx - y}{(x - 1) {}^{2}(x + 1) }$