y=3x^4-4x^3+1
y`=12x³-12x²=12x²(x-1)=0
y``=36x²-24x=12x(3x-2)=0
x=0 x=1
(-∝,0) 0 (0,1) 1 (1,+∝)
y` <0 0 <0 0 >0
单调增区间(1,+∝)
单调减区间(-∝,1)
极小f(1)=0
y``=36x²-24x=12x(3x-2)=0
(-∝,0) 0 (0,2/3) 2/3 (2/3,+∝)
y`` >0 0 <0 0 >0
凹区间(-∝,0)U(2/3,+∝)
凸区间 (0,2/3)
拐点f(0) f(2/3)