Chia đơn thức cho đơn thức

a) $8x^5 : 4x^3 = (8 : 4) \cdot (x^5 : x^3) = 2 \cdot x^2 = 2x^2$ b) $120x^7 : (-24x^5) = [120 : (-24)] \cdot (x^7 : x^5) = -5 \cdot x^2 = -5x^2$ c) $\dfrac{3}{4}(-x)^3 : \dfrac{1}{8}x = \dfrac{-3}{4}x^3 : \dfrac{1}{8}x = \left(\dfrac{-3}{4} : \dfrac{1}{8}\right) \cdot (x^3 : x) = \left(\dfrac{-3}{4} \times 8\right) \cdot x^2 = -6x^2$ d) $-3{,}72x^4 : (-4x^2) = [(-3{,}72) : (-4)] \cdot (x^4 : x^2) = 0{,}93 \cdot x^2 = 0{,}93x^2$