a*a - a - 1
a*a - a - 1 при a = 1/3
(1/3)*(1/3) - (1/3) - 1
1/(3*3) - 1/3 - 1
-11/9
2 -1 + a - a
-1.0 - a + a*a
-1 + a*(-1 + a)