1 1 --- + --- x y _________ 1 1 --- -- --- x y

diteliti lagi ya kak, barangkali ada yang masih keliru..

[tex] \frac{1}{x} + \frac{1}{y} = \frac{y + x}{xy} \\ \frac{1}{x} - \frac{1}{y} = \frac{y - x}{xy} \\ \frac{y + x}{xy} \div \frac{y - x}{xy} = \frac{y + x}{y - x} [/tex]