\[= 81 - 81 - 27 - 3a + b =\]
\[= - 3a + b - 27\]
\[P(2) =\]
\[= 2^{4} + 3 \bullet 2^{3} - 3 \bullet 2^{2} + a \bullet 2 + b =\]
\[= 16 + 24 - 12 + 2a + b =\]
\[= 2a + b + 28\]
\[(1) + (2):\ \ \ \ 3a + 2a + 27 - 7 =\]
\[= 0\]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 5a + 20 = 0\]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 5a = - 20\]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ a = - 4\]
\[Ответ:\ при\ a = - 4\ \ и\ \ b = 15.\]