Сократить дробь X+7 ------------ X2+8x+7
(x+7) / (x² + 8x + 7) =
(x + 7) / (x² + 7x + x + 7) =
(x + 7) / x (x + 7) + (x + 7) =
(x + 7) / (x + 7)(x + 1) =
1 / (x + 1)