$f(x) = 10 - 6x - 2x^2$ is strictly increasing in the . . . . . . interval.

If a function $f(x)$ is increasing in an interval $x \in [a, b]$,then which of the following will always be correct?

The function $f(x) = \tan x - x$ is:

Let $g(x) = 2f(\frac{x}{2}) + f(2 - x)$ and $f''(x) < 0$ for all $x \in (0, 2)$. Then $g(x)$ increases in

The graph of the function $f(x) = \frac{\cos x}{\cos 2x}$ in the domain $\left(-\frac{\pi}{4}, \frac{\pi}{4}\right)$ is

If the interval in which the real-valued function $f(x) = \log \left(\frac{1+x}{1-x}\right) - 2x - \frac{x^3}{1-x^2}$ is decreasing is $(a, b)$,where $|b-a|$ is maximum,then $\frac{a}{b} =$