soluzione Calcolare x2 x2 + x + 1 · [( 1 x3y + y - 1 x3y - y ) : ( 1 x3y + y + 1 x3y - y ) + 1] = = x2 x2 + x + 1 · [( 1 y(x3 + 1) - 1 y(x3 - 1) ) : ( 1 y(x3 + 1) + 1 y(x3 - 1) ) + 1] = = x2 x2 + x + 1 · [ x3 - 1 - (x3 + 1) y(x3 + 1)(x3 - 1) : x3 - 1 + (x3 + 1) y(x3 + 1)(x3 - 1) + 1] = = x2 x2 + x + 1 · [ x3 - 1 - x3 - 1 y(x3 + 1)(x3 - 1) : x3 - 1 + x3 + 1 y(x3 + 1)(x3 - 1) + 1] = = x2 x2 + x + 1 · [ - 2 y(x3 + 1)(x3 - 1) : 2x3 y(x3 + 1)(x3 - 1) + 1] = = x2 x2 + x + 1 · [ - 2 y(x3 + 1)(x3 - 1) · y(x3 + 1)(x3 - 1) 2x3 + 1] = = x2 x2 + x + 1 · [ - 1 x3 + 1] = = x2 x2 + x + 1 · - 1 + x3 x3 = = x2 x2 + x + 1 · x3 - 1 x3 = = x2 x2 + x + 1 · (x - 1)(x2 + x + 1) x3 = = x - 1 x