hộ mình bài 5 nhá chula

$a)(-2a^3b^3)^3.\dfrac{1}{8}a^2b\\ =-8a^9b^9.\dfrac{1}{8}a^2b\\ =-a^{11}b^{10}\\ \text{Hệ số:}-1\\ b)-\dfrac{1}{2}x^2y^2z^3\left(\dfrac{6}{7}xy^2\right)^2x^2z^4\\ =-\dfrac{1}{2}x^4y^2z^7.\dfrac{36}{49}x^2y^4\\ =-\dfrac{18}{49}x^6y^6z^7\\ \text{Hệ số:} -\dfrac{18}{49}\\ c)2a^5b^2c^4(-3a^4c^2)ab\\ =-6a^{10}b^3c^6\\ \text{Hệ số:}-6$