Question 1068853
Is that a typo or did you mean to write,
{{{f^2=x^2+2}}}?
If so,
{{{f(x)=sqrt(x^2+2)}}}
{{{f(6)=sqrt(6^2+2)}}}
{{{f(6)=sqrt(38)}}} or {{{f(6)=-sqrt(38)}}}
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If it was a typo,
{{{f(x)=x^2+2}}}
{{{f(6)=6^2+2}}}
{{{f(6)=38}}}