6) 2 1/4 c3d⋅(-2/3 cd2)2;

б) $$2 \frac{1}{4}c^3d \cdot (-\frac{2}{3}cd^2)^2 = \frac{9}{4}c^3d \cdot \frac{4}{9}c^2d^4 = c^{3+2}d^{1+4} = c^5d^5$$.

Ответ: $$c^5d^5$$