Question

Si a:b=c:d . Demostrar que a-1:b=bc-d:bd

Answer 1

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

despejamos a

$a= \frac{bc}{d}$

tenemos que 

$\frac{a-1}{b} = \frac{bc-d}{bd}$

remplazando el valor de a

$\frac{ \frac{bc}{d} -1}{b} = \frac{bc-d}{bd}$
 
$\frac{ \frac{bc-d}d}{b} = \frac{bc-d}{bd}$

$\frac{bc-d}{bd} = \frac{bc-d}{bd}$