Rational numbers in irrational bases

310 Views Asked by At

If you take the base-$b$ expansion of a rational number where $b$ is irrational, do you get a non-terminating sequence of digits (assuming you pick the right(?) digits)? More informally, do rational numbers look irrational in irrational bases?

1

There are 1 best solutions below

2
On

Rational numbers in decimal or binary or similar cases can have non-terminating recurring representations, for example $\frac13 = 0.3333333\ldots_{10}= 0.\overline{3}_{10}$. Presumably you want to include these

Your golden ratio base link shows that there are irrational bases in which all rationals can be represented with terminating or recurring expressions. For example $2 = 10.01_{\phi}$ and $\frac12 = 0.\overline{010}_{\phi}$

There are other bases for which this would not be the case - in particular with transcendental bases (since such a representation would imply a polynomial equation)