x log3=y log4=z log12，證明z/x+z/y=1。請教教小弟，列步驟。

x log3=z log12
z/x = log3 / log12 ----------------(1)
y log4=z log12
z/y=log4 / log12---------------(2)
(1)+(2)
z/x+z/y= log3 / log12 + log4 / log12
z/x+z/y=(log 3 +log 4)/log 12
z/x+z/y= log12/log12
z/x+z/y=1