If $\gcd(a,b)=1=\gcd(c,d)$, $b>0$, $d>0$ and $\frac {a}{b}+ \frac {c}{d}$ is an integer, show that $b=d$
Prove for positive integers a,b,c and d (where b does not equal d), if gcd(a,b) = gcd(c,d) = 1, then a/b + c/d is not an integer