f(x)=ax^3-2ax+3a-4在区间(-1,1)上有零点,
a=4/(x^3-2x+3),
设g(x)=x^3-2x+3,x∈(-1,1),则
g'(x)=3x^2-2=3(x-√6/3)(x+√6/3),
-√6/3