The proof of invertendo from $\dfrac{a}{b} = \dfrac{c}{d}$ uses the step—

Question

Accepted Answer

multiply both sides by $bd$ to get $ad = bc$, then divide by $ac$

Answer

add $1$ to both sides

Answer

subtract $1$ from both sides

Answer

take the cube of both sides

The proof of invertendo from ab=cd\dfrac{a}{b} = \dfrac{c}{d}ba​=dc​ uses the step—