(2)的单调递减区间.
15.已知函数f(x)=1/3 x^3-ax^2+4x.
(1)若曲线y"=" f(x)在点(1,f(1))处的切线的倾斜角为π/4,求实数a的值;
(2)若函数y"=" f(x)在区间(0, 1/2)上单调递增,求实数a的范围
16.已知函数,其中.
(1)讨论的单调性;
(2)若对成立,求实数的取值范围.