\[\boxed{\text{731\ (731).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ y = x² + 15\]
\[y \in \lbrack 15; + \infty).\]
\[\textbf{б)}\ y = (x - 16)²\]
\[y \in \lbrack 0; + \infty).\]
\[\textbf{в)}\ y = - x^{2} + 8\]
\[y \in ( - \infty;8\rbrack.\]