7/8 класс, алгебра. 121 (в,е)

№ 121

в)
$(x-\frac{x^2+y^2}{x+y} )*( \frac{1}{y}+ \frac{2}{x-y} )= \frac{x^2+xy-x^2-y^2}{x+y} * \frac{x-y+2y}{y(x-y)} = \frac{xy-y^2}{x+y}* \frac{x+y}{y(x-y)} =$ $=\frac{xy-y^2}{y(x-y)}= \frac{y(x-y)}{y(x-y)} =1$

е)
$(b+1- \frac{1}{1-b}):(b- \frac{b^2}{b-1})= \frac{1-b^2-1}{1-b} : \frac{b^2-b-b^2}{b-1}= \frac{-b^2}{1-b}: \frac{-b}{b-1} = \frac{-b^2}{1-b}* \frac{b-1}{-b} =$ $=\frac{b^2}{b-1}* \frac{b-1}{-b}= \frac{b^2}{-b}=-b$