Decreasing function depending in parameters

199 Views Asked by At

Consider :

  • $\alpha$ , $\lambda$ and $\rho$ $\in \mathbb{R}$
  • $\alpha$ $\geq$ - $\frac{1}{2}$
  • $a=\alpha$ + $\frac{1}{2}$ and $b=\frac{\lambda^2}{2(\alpha+1)}$
  • a function $f(x)\in \mathbb{R}$ , $x>0$

  • $f$ is decreasing to $2\rho$

    ie: $f$ is decreasing and $$\lim_{x\rightarrow\infty} f(x) = 2\rho\; \forall x > 0.$$

Consider a function $H:$ $$H(x) = \frac{a}{x} - \frac{1}{2}f(x) - b\ , \forall x > 0.$$

I need to know:

  • in which cases $$\exists\ c \in \mathbb{R}\ : H(x) < c\ , \forall x > 0.$$
  • in these cases what are the values of $c$ ?

Thanks.

Update

$$f(x) = \frac{2 \alpha + 1}{x} + \beta(x)\ , \forall x > 0.$$

where $\beta$ is a function and $\beta(0)=0$