ax^2 + (a-1)x + a-1< 0
x^2 + (a-1)x/a < (1-a)/a
x^2 + (a-1)x/a + [(a-1)/(2a)]^2< (1-a)/a + [(a-1)/(2a)]^2
[(x + (a-1)/(2a)]^2 < (1-a)/a + [(a-1)/(2a)]^2
因为 [(x + (a-1)/(2a)]^2 ≥ 0
所以 (1-a)/a + [(a-1)/(2a)]^2 ≤ 0
(1-a)/a + (a-1)^2/(4a^2) ≤ 0
两边同乘以
4a(1-a) + (a-1)^2 ≤ 0
4a - 4a^2 + a^2 -2a +1 ≤ 0
2a - 3a^2 +1 ≤ 0
3a^2 -2a -1 ≥ 0
再往下你自己应该会解了?