Giải thích các bước giải:
a.Ta có:
$4^9:5^{27}=\dfrac{4^9}{5^{27}}=\dfrac{4^9}{5^{3\cdot 9}}=\dfrac{4^9}{\left(5^3\right)^{9}}=\dfrac{4^9}{125^{9}}=\left(\dfrac{4}{125}\right)^9$
b.Ta có:
$27^5:\left(-7\right)^{15}=\left(3^3\right)^{5}:\left(-7\right)^{15}=3^{3\cdot 5}:\left(-7\right)^{15}=3^{15}:\left(-7\right)^{15}=\left(\dfrac{3}{-7}\right)^{15}=-\left(\dfrac{3}{7}\right)^{15}$
c.Ta có:
$8x^3:\left(4x^2\right)=\dfrac{8x^3}{4x^2}=\dfrac{2x\cdot 4x^2}{4x^2}=2x=\left(2x\right)^1$
