Question 13: Which of the following functions is always inverse on each of its definite intervals D?

– With the function \(y=\frac{{8 – x}}{{x + 3}}\) We have:

\(\begin{array}{l} TXĐ:D =\mathbb{R} \backslash {\rm{\{ – 3\} }}\\ \Rightarrow f'(x) = \frac{{-11} }{{{{\left( {x + 3} \right)}^2}}} < 0\,\forall x \ne - 3 \end{array}\)so the function is inverse on its definite set.