Объяснение:

1)

[tex] - 2mn ^{2} \times ( - 9m^{5} n) = ( - 2 \times - 9) + (m \times m ^{5} ) + (n { \times n}^{2} ) = 18 {m}^{6} n ^{3} [/tex]

2)

[tex]8x {5} \times ( \frac{ - 1}{8} xy) =-8 {x}^{5} \times \frac{1}{8} xy = - {x}^{5} \times xy = - {x}^{6} y[/tex]