### On the bounds of zeroth--order general Randic index

#### Abstract

The zeroth--order general Randi\' c index, $^0\!R_{\alpha}(G)$, of a connected graph $G$, is defined as $^0\!R_{\alpha}(G)=\sum_{i=1}^{n}d_{i}^{\alpha}$,

where $d_{i}$ is the degree of the vertex $v_{i}$ of $G$ and $\alpha$ arbitrary real number. We consider linear combinations of the

$^0\!R_{\alpha}(G)$ of the form $ ^0\!R_{\alpha}(G) - (\Delta +\delta) ^0\!R_{\alpha -1}(G)+ \Delta\delta\, ^0\!R_{\alpha-2}(G)$ and

$^0\!R_{\alpha}(G)- 2a\,\, ^0\!R_{\alpha-1}(G)+ a^2\,\,{^0\!R_{\alpha-2}(G)}$, where $a$ is an arbitrary real number, and determine their bounds. As corollaries, various upper and lower bounds of $^0\!R_{\alpha}(G)$ and indices that represent some special cases of $^0\!R_{\alpha}(G)$ are obtained.

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