10 y² 1-2y y-1 1-y

10. $$ \frac{y^2}{y-1} - \frac{1-2y}{1-y} = \frac{y^2}{y-1} + \frac{1-2y}{y-1} = \frac{y^2+1-2y}{y-1} = \frac{y^2-2y+1}{y-1} = \frac{(y-1)^2}{y-1} = y-1 $$

Ответ: $$y-1$$