\[P(3) =\]
\[= 3^{4} - 3 \bullet 3^{3} + 2 \bullet 3^{2} + a \bullet 3 + b =\]
\[= 81 - 81 + 18 + 3a + b =\]
\[= 3a + b + 18\]
\[P(2) =\]
\[= 2^{4} - 3 \bullet 2^{3} + 2 \bullet 2^{2} + a \bullet 2 + b =\]
\[= 16 - 24 + 8 + 2a + b =\]
\[= 2a + b\]
\[(1) + (2):\ \ \ 3a - 2a + 18 - 15 =\]
\[= 0\]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ a + 3 = 0\]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ a = - 3\]
\[Ответ:\ при\ a = - 3\ \ и\ \ b = - 9.\]