What is the nature of the function $$f(x)=x^3-3 x^2+4 x$$ on real numbers?

$$ \text { If } f(x)=\frac{a \sin x+b \cos x}{c \sin x+d \cos x} \text { is decreasing for all } x \text {, then } $$

$$ \text { The function } y=\tan x-x \text { is } $$

If $$f(x)=\log x+b x^2+a x, x \neq 0$$ has extreme values (or turning points) at $$x=-1$$ and $$x=2$$ then the values of $$\mathrm{a}$$ and $$\mathrm{b}$$ are