I am a bit stuck on this problem. Here is how I've approached it:Let $\displaystyle m= \frac{y}{x+1}$. Prove that if m is rational, then x and y must also be rational.

Let $\displaystyle m= \frac{c}{d}$. Then $\displaystyle \frac{c}{d} = \frac{y}{x+1}$

Then from here I don't know what to do. We can't express x or y solely in terms of c and d. And expressing x in terms of c, d and y (or y in terms of c, d and x) is inconclusive because we cannot assume that y and x respectively are rational, as that is what we are trying to show.

Any help, please? Many thanks!