Giải thích các bước giải:
$\dfrac{a}{b}$ $-$ $\dfrac{c}{d}$ $=$ $\dfrac{a}{b}$ $.$ $\dfrac{c}{d}$ $⇔$ $\dfrac{ad - bc}{bd}$ $=$ $\dfrac{ac}{bd}$ $⇔$ $ad - bc = ac$
$⇔$ $ad = ac + bc$ $⇔$ $ad = c(a + b) ⇔$ $\dfrac{c}{d}$ $=$ $\dfrac{a}{a + b}$
$\text{#Annihilators}$