# Triple derivative cubic

Calculus Level 3

$f(x)=x^{3}+bx^{2}+cx+d$ is a monic cubic function . For real $$a,b,c$$ and $$x$$ .

If $$\sqrt{f'''(x)}< \sqrt{x^{2}+bx+3}$$ .

Then , the value which $$b^{2}-4b$$ cannot take from given options is ::

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