要过程
0 ≥t^3-5t^2+12
t^3-5t^2+12=(t^3-2t^2)-(3t^2-6t)-(6t+12)=(t^2-3t-6)(t-2)=[t-(3+√33)/2][t-(3-√33)/2](t-2)<=0
再用逐根法就可以了
(-∞,(3-√33)/2)∪(2,(3+√33)/2)