a: \(\dfrac{5}{3x}=\dfrac{5\cdot2}{3x\cdot2}=\dfrac{10}{6x};\dfrac{-4x}{2}=\dfrac{-4x\cdot3x}{2\cdot3x}=\dfrac{-12x^2}{6x}\)
b: \(\dfrac{5}{4x^2}=\dfrac{5\cdot x}{4x^2\cdot x}=\dfrac{5x}{4x^3};\dfrac{-2}{2x^3}=\dfrac{-2\cdot2}{2x^3\cdot2}=\dfrac{-4}{4x^3}\)
c: \(\dfrac{7x}{4a}=\dfrac{7x\cdot b}{4a\cdot b}=\dfrac{7xb}{4ab};\dfrac{84}{2b}=\dfrac{84\cdot2\cdot a}{2b\cdot2a}=\dfrac{168a}{4ab}\)
d: \(\dfrac{b}{6a}=\dfrac{b\cdot3b}{18ab}=\dfrac{3b^2}{18ab}\)
\(\dfrac{4}{18ab}=\dfrac{4\cdot1}{18ab}=\dfrac{4}{18ab}\)
\(\dfrac{x}{9b}=\dfrac{x\cdot2a}{9b\cdot2a}=\dfrac{2ax}{18ab}\)
e: \(\dfrac{7}{30x^3y^3}=\dfrac{7\cdot x}{30x^4y^3}\)
\(\dfrac{6}{5x^4y^3}=\dfrac{6\cdot6}{5x^4y^3\cdot6}=\dfrac{36}{30x^4y^3}\)
\(\dfrac{13}{6x^2y^3}=\dfrac{13\cdot5\cdot x^2}{6x^2y^3\cdot5x^2}=\dfrac{65x^2}{30x^4y^3}\)
