Ответ: \displaystyle \dfrac{a}{b}\displaystyle + \frac{a-1}{a}: \frac{a+b}{ab}= \frac{a}{b}+ \frac{a-1}{a}\cdot \frac{ab}{a+b} = \frac{a}{b}+ \frac{b(a-1)}{a+b} =\\ \\ = \frac{a^2b+b^2a+ab^2-b^2}{a+b} = \frac{2ab^2+a^2b-b^2}{a+b} Если a=0.2;~~~b=0.3 то \displaystyle \frac{2\cdot 0.2\cdot 0.3^2+0.2^2\cdot 0.3-0.3^2}{0.2+0.3}= -0.084
Источник znanija.site