\[\boxed{\mathbf{311}.}\]
\[P(x) = M_{1}(x)(x + 4) + 5\]
\[P(x) = M_{2}(x)(x - 5) + 14\]
\[P(x) = M_{3}(x)(x + 4)(x - 5) +\]
\[+ ax + b\]
\[x = - 4:\]
\[P( - 4) = 0 \cdot M_{1}(x) + 5 = 5;\]
\[P( - 4) = 0 \cdot M_{3}(x) - 4a + b =\]
\[= - 4a + b.\]
\[x = 5:\]
\[P(5) = 0 \cdot M_{2}(x) + 14 = 14;\]
\[P(5) = 0 \cdot M_{3}(x) + 5a + b =\]
\[= 5a + b.\]
\[\left\{ \begin{matrix} - 4a + b = 5 \\ 5a + b = 14\ \\ \end{matrix} \right.\ ( - )\]
\[- 9a = - 9\]
\[a = 1.\]
\[b = 5 + 4a = 5 + 4 = 9.\]
\[Ответ:\ \ x + 9.\]