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Решите задачу:

$\frac{-12xy^2}{5z^4t^{10}}\cdot \frac{25z^8t^2}{18xy}=-\frac{12\cdot 25}{18\cdot 5}\cdot \frac{y^2}{y}\cdot \frac{z^8}{z^4}\cdot \frac{t^2}{t^{10}}=-\frac{2\cdot 5}{3}\cdot y\cdot z^4\cdot \frac{1}{t^8}=-\frac{10yz^4}{3t^8}\\\\\\\frac{x^3y-4x^2}{8y^2}\cdot \frac{2y}{x^2y-4x}=\frac{x^2(xy-4)}{8y^2}\cdot \frac{2y}{x(xy-4)}=\frac{x}{4y}\\\\\\-(\frac{2a^3b}{c^2})^5=-\frac{32a^{15}b^5}{c^{10}}$