Question

Срочно!Дам 90 баллов

Answer 1

Ответ:

$\displaystyle \frac{x}{x-1}+\frac{x}{x+1}=\frac{x(x+1)+x(x-1)}{(x-1)(x+1)}=\frac{x^2+x+x^2-x}{x^2-1^2}=\frac{2x^2}{x^2-1}\\\\\\\frac{a-b}{ab^2}-\frac{b-a}{a^2b}=\frac{(a-b)\cdot a-(b-a)\cdot b}{a^2b^2}=\frac{a^2-ab-b^2+ab}{a^2b^2}=\frac{a^2-b^2}{a^2b^2}\\\\\\\frac{y^2-y}{2xy}\cdot \frac{2x}{y^2-1}=\frac{y(y-1)}{2xy}\cdot \frac{2x}{(y-1)(y+1)}=\frac{1}{y+1}\\\\\\\frac{c+7}{2b}:\frac{49-c^2}{4b^2}=\frac{c+7}{2b}:\frac{(7-c)(7+c)}{4b^2}=\frac{c+7}{2b}\cdot \frac{4b^2}{(7-c)(c+7)}=\frac{2b}{7-c}$