If $\dfrac{a}{b} = \dfrac{c}{d}$, by invertendo we get—

Question

Accepted Answer

$\dfrac{b}{a} = \dfrac{d}{c}$

Answer

$\dfrac{a}{c} = \dfrac{b}{d}$

Answer

$\dfrac{a+b}{b} = \dfrac{c+d}{d}$

Answer

$\dfrac{a-b}{a+b} = \dfrac{c-d}{c+d}$

If ab=cd\dfrac{a}{b} = \dfrac{c}{d}ba​=dc​, by invertendo we get—