\[x^{2} \cdot \left( - \frac{1}{8} \right) \cdot y^{2}xy = - \frac{1}{8}x^{3}y^{3};\]
\[x = 1;\ \ y = 2:\]
\[- \frac{1}{8} \cdot 1^{3} \cdot 2^{3} = - \frac{1}{8} \cdot 8 = - 1.\]