圖像關(guān)于原點對稱,
f(-x)+f(x)=2bx^2+2d=0,
b=0,d=0,
f(x)=ax^3+cx.
f’(x)=3ax^2+c=0
x^2=-c/3a=1
c=-3a
f (1)=a+c=a-3a=-2a=-2,
a=1,c=-3,
f(x)=x^3-3x.
f’(x)=3x^2-3=0,
x=±1,
x>1,f’>0,f單增；
-1≤x≤1,f’≤0,f單減；
x0,f單增.
2.
x^3-3x＞5mx²－﹙4m²＋3﹚x
x(x-m)(x-4m)>0
當m=0時,x>0;
當m>0時,0