\[(x + 1) \cdot \ *\ = x^{2} + 3x + 2\]
\[x^{2} + 3x + 2 =\]
\[= x^{2} + x + 2x + 2 =\]
\[= x(x + 1) + 2 \cdot (x + 1) =\]
\[= (x + 1)(x + 2)\]
\[(x + 1) \cdot \ *\ = (x + 1)(x + 2)\]
\[\Longrightarrow \ *\ = x + 2.\]